Good:
Going with others with Mithos in Tales of Symphonia. My all-time favorite RPG (I know, it ripped off everyone, but it did it well and with a great battle system), and Mithos's story was so sad and lonely, I felt bad for him.

The final boss in Beyond Good and Evil. I forget what he was called, but that boss was damn hard, especially the very last portion with the confusion. It took me about a half hour to beat it and as soon as I had, I jumped up and yelled, "Gotcha, bitch!" It was a great feeling. :D

Baaah, I'm a sheep; GlaDOS. I replay it all the time just to listen to her. She's hilarious.

Bad:
Ganon(dorf) in any 3D Zelda. I beat the Twilight Princess one in a minute. Zant would have been a cooler last boss.

The comet in Illusion of Gaia. I haven't played the game since I was a kid, but I very distinctly remember feeling disappointed.

Rage-Inducing:
Zophar in Lunar 2: EBC. Okay, let's get something straight game developers. I know that final battles in character-driven RPGs have to be emotional and epic and all. That does not mean you undermine hours of work I've put into all of my party and then take them away from me in the final battle for plot purposes. There was no reason for it! My party was right behind me! Why weren't they fighting with me? Why was I stuck with a useless mage who I couldn't even control? NOT COOL. I DO NOT APPROVE. :( :( :(

For good boss battles, I'd say KH (1 and 2), and I liked how you could a charismatic character actually win. Glados isn't hard but damn funny, and I actually loved the end battle of Ep2.

As for bad encounters, I'll have to say Halo 3's was a massive cock-slap. Yeh, I don't play many games with boss battles.

Not an end boss as such, but still good: That drugged-up crazy satanist bastard in Max Payne (his name escapes me at the moment- it's been quite some time since i played it.) He was a giant pain in the arse, mostly for all the minions he sent at your first before appearing himself. Being high as a kite, he could take a hell of a lot of damage before he died, and his ranting was genuinely unsettling, after finding all the occult stuff on your way up to him. I half expected him to turn into some kind of demon-possessed uber monster type (which would have been a bit out of character for the game, admittedly.) The satisfaction at killing him was tremendous.

Bad boss? The final boss of Half Life was a bit of a let down (actually the whole Xen bit was a bit of an anti-climax.)

Good boss: Liquid from MGS4 that is an awsome battle especially on higher difficulties it gets so hard

Bad boss: the first stalker from resistance fall of man it to easy to take it down in my opinion

Good Boss= The end boss in Portal is definately the best. Made me laugh throughout.
Bad Boss= The cartographer in Halo 3. Way too easy and seemed like an anticlimax as i had played 3 halo games just to fight a pitiful villain.

hix24:
Bad Boss= The cartographer in Halo 3. Way too easy and seemed like an anticlimax as i had played 3 halo games just to fight a pitiful villain.

I think the point of the last "boss" in Halo 3 was just to let people catharsise by shooting the fuck out of 343 Guilty Spark, the smug annoying little git. The real climax was that drive to the end, which was awesome.

MASSIVE SPOILER
Good End Boss: Persona 3 - Nyx Avatar (if you're at level 70-75 :P) - Literally, Death Incarnate. massively powerful attacks, but not so powerful he's impossible, a huge amount of HP, and an amazing in-battle dialogue that touches on every character throughout the game, this boss defines the epic battle, someone so strong that to defeat it, you must sacrfice yourself. The mood is kinda killed if you go past level 85 though, because then he doesn't really threaten you too much, but that would require some extensive grinding.

Bad End Boss: Sephiroth - FF7: moreso because Final Fantasies always allow you to become hilarious overpowered, even without level grinding and sidequests. What a pushover. :(

Threadbare:

Bad Boss:
Fable's Jack of Blades.
Whoops, anticlimax.

Yeah, laaaaaame

Good:
Phantasy Star I

Skies of Arcadia - Sort of the same effect as the PSI and to some extent KH2, the bosses just keep coming but never diminish in awesomeness.

windfish:

The Nightmares from Link's Awakening
Last swordfight of Twilight Princess

Also, Golden Sun: The Lost Age's last boss (although...distinctly unoriginal) is a really awesome fight.

I think i've based these more on the EPIC factor than anything else...

Devil May Cry 2: Yes, the game is crap... but the last boss is literally all of the games bosses put together in a huge, disgusting blob and it attacks you.

Crysis: Good would have been calling it quits going solo on that giant tentacle monster, bad is the actual killing of that large weird thing that was just annoying and you got to use a one shot, one kill weapon. Lame.

Best: Tales of Destiny 2. You have to pull off an EXACT combo at the EXACT moment to kill the final boss, but OMG is it a bad-ass move and have sweating feverishly to beat that last boss it was one of the best "YES!!!!!" Moments.

I cant think of any more great bosses just this moment, that's sad :(

Good end boss: Penance from FFX. Not the end boss of the plot but the ubre-end-boss for being so damn far into the game you can effectively challenge him. You can be max level with everybody and still struggle, even if you know what you are doing against him (and don't use the overdrive of a particular aeon to insta-kill him, or have any armor with insta-reraise).

Bad end boss: The flying fortress from the first AC game. Too easy tbh.

TheKbob:

Best: Tales of Destiny 2. You have to pull off an EXACT combo at the EXACT moment to kill the final boss, but OMG is it a bad-ass move and have sweating feverishly to beat that last boss it was one of the best "YES!!!!!" Moments.

Reminds me of another good end boss: The Time Devourer from Chrono Cross. Defeating him the "right way" was a matter of precise timing and strategy, and it felt great to finally get everything right and use the Chrono Cross.

Good-GLaDoS, Portal. Not petically difficult, but so so funny. Some of the best lines in portal are in the boss fight.

Bad-Bowser, Mario Galaxy....Thats...that it! That was nothing!?!

Good

Dr. Wily (Mega Man 7) - An extremely challenging boss fight that requires extremely good timing, endurance (you have to hit him with about 28 fully charged Mega Buster shots to beat him) and some stylish dodging to survive. It doesn't feel cheap either, as you can take 5-6 hits before dying. The kickass boss fight is followed by a kickass ending as well.

Sanctus Diabolica (Devil May Cry 4) - Not a particularly challenging boss fight, once you learn how he telegraphs his attacks, but it is hella fun to Falcon Punch him all those times with the Buster.

Bad

Gill (Street Fighter 3: 3rd Strike) - First of all, he looks friggin' ridiculous. Long blond hair, his left side is blue, and his right side is red. And he's completely naked, save for a little thong/loincloth thing. Second of all: "The mark of my dignity shall scar thy DNA." What. The. Fuck. Third, that damn resurrection move. He comes back to life and fully heals himself while some aura pushes you back to prevent you from interrupting his healing? Ridiculous.

Good:
Hybrid Heaven for the N64 was pretty much my first RPG, if it even counts as one. I haven't played it in a long time, but I remember being absolutely enthralled by the climax, which involved fights with:
Two NPCs who have been major antagonists throughout the game;
The evil overlord of the invading alien bodysnatchers;
The evil alien bodysnatcher which is actually an entirely different alien bodysnatcher and has two separate forms to beat you up with;
and Diaz, the guy you were disguised as when the game started, who is determined to kill you because of what you've done to his reputation thanks to the things you did when people thought you were him!
Throughout the first five battles I had been saving up all of the Shot weapons (I'm a hoarder like that). I'd tried them against the bodysnatcher but as I recall they didn't work because he was psychic. So anyway, I run into Diaz, who is obsessed with defeating me hand-to-hand in single combat. And I just hit him with every Shot I had and he went down. It was hilarious.

My most favourite boss recently is Zeus from God Of War 2. The music, mroe than anything, is awesome. Only bad part was, he survived the fight.

Worst? Metroid Prime 2. It's a fairly hard boss, as are all of that game's bosses, and it's on a fucking timer. No, thank you, I'll just Action Replay past that if you don't mind.

I also disliked Mithos in Tales Of Symphonia. I know every JRPG has to have the "It's over... no it's not!" twist at the end, but there was no reason for why Mithos suddenly turned into a giant robot. It just mae me roll my eyes.

Final Fantasy X also has a terrible final boss, because it isn't a final boss. Tidus's monster father was the final boss, the rest was just a cutscene where everyone was suddenly invincible for some reason.

I signed up simply to express my disappointment in the fact that no one mentioned King Bohan from Heavenly Sword. In all honesty, it's one of the hardest, most annoying and yet beautiful and ultimately rewarding boss fights I've seen in any game for the PS3.

As for bad boss fights, there's a small bunch.

" Tabuu from SSBB. This guy annoyed the shit out of me and my friend when playing co-op. Although we killed him, we have yet to find a way to dodge his flashy hit-anything-on-the-map attack.

" Ocelot from MGS4. Sure, the fight had plenty of surprises, but it was just too damn easy and out of character.

" The obvious Elder Scrolls "bosses".

Good Boss: Tabuu from SSBB. He's rough to fight, and he's got an attack that's completely unaviodable. Even though he's a complete ripoff of Nightmare from the Kirby Series, and a real bitch when you're trying to get his trophy.

Bad Boss: Mysterio from Spiderman 2. There's this gigantic scene that's supposed to lead up to a big boss fight (but why would an alien rob a deli to begin with? That never made sense.), and it takes one right hook to kill him. Talk about an anticlimax.

Best boss fight: Kefka. An awesome song the whole way through and you have to fight a tower of doom just to get to him? Then when you do he's some kind of angel? Amazing.

Bad boss fight: Metal Gear RAY in MGS2. Come on I fought Vamp a bunch of times already, why can't I just mow down Metal Gears? What do you mean you can't win? THEY'RE TOO DAMN EASY. LETS DESTROY THEM ALL! Jesus.

masterem243:
Bad Boss: Mysterio from Spiderman 2. There's this gigantic scene that's supposed to lead up to a big boss fight (but why would an alien rob a deli to begin with? That never made sense.), and it takes one right hook to kill him. Talk about an anticlimax.

That was the point of that boss fight. It was a joke. As for why he was robbing a deli, it was because he was a laughable villain throughout the entire game. He's not an alien; he's a special-effects guru who was made a fool of by Spiderman.

See, the setup occurs when you run in and he's robbing the place. Then there's the cutscene where he talks about how much of your ass he's going to kick, and his life bar fills up five times over. This is all setup, and, as you say, it's building expectations for a challenging and hard boss battle. Then you run up to him and punch him once. And the life bar completely empties straight away. That is the punchline, wherein the expectations are confounded. It is called the "punch" line because, like being punched in the face, it's a surprise. Here is a wikipedia article containing information on the game's story: http://en.wikipedia.org/wiki/Spider-Man_2_%28video_game%29#Plot

Housefly:

masterem243:
Bad Boss: Mysterio from Spiderman 2. There's this gigantic scene that's supposed to lead up to a big boss fight (but why would an alien rob a deli to begin with? That never made sense.), and it takes one right hook to kill him. Talk about an anticlimax.

That was the point of that boss fight. It was a joke. As for why he was robbing a deli, it was because he was a laughable villain throughout the entire game. He's not an alien; he's a special-effects guru who was made a fool of by Spiderman.

See, the setup occurs when you run in and he's robbing the place. Then there's the cutscene where he talks about how much of your ass he's going to kick, and his life bar fills up five times over. This is all setup, and, as you say, it's building expectations for a challenging and hard boss battle. Then you run up to him and punch him once. And the life bar completely empties straight away. That is the punchline, wherein the expectations are confounded. It is called the "punch" line because, like being punched in the face, it's a surprise. Here is a wikipedia article containing information on the game's story: http://en.wikipedia.org/wiki/Spider-Man_2_%28video_game%29#Plot

I understand that whole thing, but he was supposed to be disguised as an intergalaxial conqueror. Now, if you were going to keep that persona for as long as possible, why would you bother to rob a deli, instead of lighting things on fire and blowing up major landmarks? I found it to be an anticlimax, and wasn't all that funny. Then again, most video game adaptations of movies are laughable to begin with.

Good Boss:
-Laughing Octupus(MGS4) - It was a big game of Hide and Seek, and her different disguises were great too.
-Liquid Ocelot(MGS4) - This fight had great little details like your life gauge corresponding with which games music is playing and Liquid Ocelot changing into his version from those games.
-Van(Tales of the Abyss) - People mentioned Mithos/Yggdrasil from Tales of Symphonia but I never had any sympathy for him and the battle system was more refined in Tales of the Abyss.

Bad Boss:
-Tabuu(SSBB) - He came out of nowhere and his moves were extremly powerful.
-Final Fantasy X - The reason has already been said multiple times.

Good End bosses...
From Mass Effect, the Sareaper. A little disappointing that you don't get to fight an avatar of Sovereign on the bridge, or something like that, but this works nicely. You wanted to kick both their asses the whole game long, and here's your chance to do it.

The worst? Sword-wielding Ganondorf at the tail-end of Twilight Princess. Easy, not epic enough, not challenging enough. That, or Master Hand.

What I didn't like about that fight with Ganondorf was the way he just trudged around the arena like he'd soiled himself. If he'd been leaping about like he was at the end of Wind Waker (and a touch harder) that'd have been awesome.

Indigo_Dingo:

Geo Da Sponge:

Destroy All Humans 2: Fighting Premier What's-his-name on the moon. Hideous and unimaginative, like most of Destroy All Humans 2 compared to the original. Also, it was way too easy. Seriously, I defeated him on my first try within five minutes, no problem. I mean there's fairly easy, and then there's 'broken' easy. Easier than 343 Guilty Spark, on easy mode, in a game were normal is already the equivalent of easy in other games.

It's just that easy.

Screw that, I beat the guy in 20 seconds. i froze time and shot him - he couldn't regenerate, and was just instantly killed.

Well, really it wasn't five minutes, but that seems like the amount of time you should say if you mean 'A short period of time', whether or not it is more or less than the actual amount of time. But you probably did do it faster than me because I stood behind a pillar and said "Wait, can he get me here? No? Why not?". It sounds like you were more prepared to pull out the dirtiest ricks in the game straight away than muck around.

Good-
Malak from KOTOR since you actually hate him since he destroys a planet yet he never has the guts to actually face you head on he always sends minions or turns on turrets and retreats. satisffying fight in the end though
Seymour from FFX - again on the basis that you actually gain a dislike for him even if he is kinda cool
FFVII - ultima weapon (i think... the black one) attacks you out of the blue and proceeds to kick your ass. flees as well adding to detest of it

Bad-
Dark Sector - the colussus, it follows you for like 2-3 levels in a sort of if it catches you you're in serious trouble way.then all you do is fire glaive spam him ALOT
BF bad company - rockets v heli tada there goes the worlds greatest merc easily. then for a stpid dramatic effect he comes out the wreckage (dont know how to spoiler tag) as if theres gonna be a sequel? there cant be and i hope there isnt
LoZ twilight princess - Zant or whatever hes called goes from prince of darkness to a crazy dumass who mimicks bosses so you dont need to think what to do
Halo 3 - how to make a sub par game worse (other ones were allright but thirs can burn in the bargain bin)

Good: Malak from KOTOR, Bowser in Super Mario 64 (sure, you fight him the same way three times in a row, but the way the battles worked and new twists in each match were innovative and interesting back then), Dan and then Cecil from Operation: Winback

Bad: Bowser from Paper Mario. The next to last boss, the Crystal guy, was challenging and actually required some tactics. Bowser had like two attacks and was just bland turn based bullshit. Not to mention the side fight you had to endure as Peach against Kammy Koopa. Blugh.

Any boss who is invulnerable except for a short, randomized section is bad. I believe General RAAM was like this, because I can't recall any sure tactic to make the Krylll fly away from him.

That Skedar at the end of Perfect Dark sucked.

Oh and heres an obscure one: Satan in the Game Archangel; You have a sword which is practically a pubic hair from god, through out the game it drains to much mana to use, at the end boss all you do is use to open a door and thats it.

As for the DMC2 endboss, that was one of the easiest bosses to predict, my only difficulty I had was the oversized healthbar.

Poor Dagon. He's not a bad final boss. He's the best final boss the game didn't let us fight.

My favourite final battle to date is the duel between Naked Snake and The Boss. Less a challenging fight as it is completely beautiful.

On the other end, there's the gigantic anticlimax of a boss at the end of Halo 3. Seriously. What?

As I previously said, the MGS series is good at the whole boss battle, excluding the fury, which to me felt like Vulcan Raven Lite.

Fav end boss: Entire final battles in chrono trigger (queen zeal 1, mammon machine, Zeal 2, Lavos 1,2,3). Fighting all those one after another really gave a sense of a long and epic battle, and they were generous to give you times to switch up party members and heal and what not. lavos was also challenging, but not to the point of absolute frustration. The entire battle just felt epic, fun, and a good balance of strategy and challenge.

Gannon from OoT was another good boss fight, had that same feeling as Chrono Trigger to me.

least fav: Ruby and Emerald weapons from FF7. As much as i love the game and the battles are pretty hard, emerald was a complete bitch with it's crusher mover, and Ruby would just shoo off your party members screwing you over if you didn't know what to do.

Bad end boss: Fontaine from Bioshock. He was basically a combination of the two kinds of big daddies, was extremely patterned, and boring. Also, he was too easy. I had to turn the difficulty to hard to feel I was even fighting a last boss.

Indigo_Dingo:

Geo Da Sponge:

Indigo_Dingo:

Geo Da Sponge:

Destroy All Humans 2: Fighting Premier What's-his-name on the moon. Hideous and unimaginative, like most of Destroy All Humans 2 compared to the original. Also, it was way too easy. Seriously, I defeated him on my first try within five minutes, no problem. I mean there's fairly easy, and then there's 'broken' easy. Easier than 343 Guilty Spark, on easy mode, in a game were normal is already the equivalent of easy in other games.

It's just that easy.

Screw that, I beat the guy in 20 seconds. i froze time and shot him - he couldn't regenerate, and was just instantly killed.

Well, really it wasn't five minutes, but that seems like the amount of time you should say if you mean 'A short period of time', whether or not it is more or less than the actual amount of time. But you probably did do it faster than me because I stood behind a pillar and said "Wait, can he get me here? No? Why not?". It sounds like you were more prepared to pull out the dirtiest ricks in the game straight away than muck around.

The game had been dissapointing up to that point, I really just wanted to get it over with. And if a game isn't prepared to actually try to stop you from pulling tricks, then the battle is bad.

Really, after the Godzilla battle it all kinda went downhill. You have a battle with a giant monster in your spaceship, staying tethered to life support while firing missiles at it, and that was great. but afterwards? Nothing even tried to compare.

The last boss sucked, I beat him in 30 seconds, but for extra challenge, I beat godzilla on foot

The Nihilanth of Half-Life 1.

"YOUU CANNOT WIIIINNNN."