BishopofAges:
To be honest and forward to your question "what made me say 'wow' about a game even before I have a chance to play it?" Actually the game isn't out yet, but Bioshock: Infinite. The trailer and all of its gooey goodness made me 'wow' by the first minute.

I know what you mean, especially the part in the E3 (?) Gameplay Video where the player character

If it truly can deliver something like that SO nonchalantly than it's pretty much set for GOTY already

WoW. Seriously.

It was a well made game. Every RPG I played after that hasn't been able to match the experience.

The demise of JRPGs isn't helping things - that used to be my favorite genre.

Uncharted 3. There were some sequences that really amazed me. Not exactly what I expected from Nate's third adventure, but surely this game includes some really cool stuff.

Baldur's Gate. I'm just playing it for the first time and I got a swift boot up the arse with the difficulty, especially when compared to most modern games that I'm familiar with. Made me say "wow" seeing how brutal it treats you, but that's a good thing.

Halo CE, amazed how annoying it gets on the last 3 chapters (it's not a good thing). I thought I liked Halo CE but I guess not that much after replaying it. Ranting aside, the lag while playing it on a 360 made it unbearable (it's not CEA).

Team Fortress 2. I saw a sniper being ubered. In a pub map with instant respawn. I was amazed, and then I instantly face-palmed right after.

Dead Space 2 had two for me. The train sequence was awesome and then the whole 'boosting through space set-piece', while simplistic just felt badass, especially with the transmissions that were coming through just before.

Before that it would have been either the flying desert snake thing in Shadow of the Colossus or my first match of Battlefield 2.

Portal 2. Certain parts of that game still give me chills. It also made me a fan of Stephen Merchant :) still dreadfully unamused by Ricky Gervais though.

To be fair, it was Assassin's Creed Brotherhood. It was the first game I ever played on my 360, and I was blown away with all the side missions and collectibles and just the sheer size of the map. You could go wherever you want and do whatever you want, the game didn't slap you on the wrist and tell you you HAVE to do this NOW. Even now, Brotherhood is the only game I genuinely am going out of my way to get every achievement and 100% sync.