People are wondering why I've decided to hate Mass Effect 3 before it even comes out. Well, I don't. I'm concerned that it might disappoint, because I like the series and want to see it live up to the amazing potential set up in the first game. To figure out where this concern comes from, let's look at the plot of the previous game. You will be required to withhold your nerd rage until the end.
Note that the rest of this article is going to be complete spoilers for the game. Stop right now if you haven't played Mass Effect 2, but plan to someday.
Mass Effect 2 opens with the death of Commander Shepard. This is an inept way to begin a story. Shepard dies, there's a cutscene, and he's alive again. Begin tutorial. Note how Spock, Gandalf, and Dumbledore didn't die at the start of any movie. If you do kill a character in the opening scene, then you'd expect the game to be that character working through the experience and growing as a human being. But Shepard is up and capping robots in seconds, and the whole "I was dead" thing has no impact on him as a character.
In the previous Mass Effect, Cerberus was a clueless, fumbling terrorist organization. At one point they fed colonists to the thresher maw in order to test the effects of feeding colonists to a thresher maw. Supposedly pro-human, they murdered, stole, and destroyed without benefiting humanity in any way. Their victims were all human. This is like a white supremacist group who only kills white people. Their plans made no sense and they were basically clueless mooks to be killed for XP.
In the second game, Cerberus is an all-powerful organization of super-brains. They bring you back from the dead. They build a ship better than the previous Normandy, which was the most advanced ship in the galaxy. They know more about the Collectors (the bad guys) than all other races combined. They claim that all of the Cerberus agents you encountered in the previous game were "rogue elements," but that doesn't make any sense because this new Cerberus is both too competent and too focused to have countless rogue cells wasting resources and working counter to Cerberus goals.
The Alliance refuses to help you, because you're working for Cerberus. And you have to work for Cerberus because the Alliance won't help you. Even your own dialog tree works against you. If you select the, "I'm not working for Cerberus" dialog option, Shepard says, "I'm working for Cerberus because [excuse]." It's a ham-fisted mess of circular logic and railroading.
Then we get to the "trap." The Collectors set aside their important collecting work to set an obvious trap for one guy. Their trap depends on Shepard being an idiot and personally boarding their vessel, instead of blasting the ship at a distance or sending in a team of subordinates. Then Shepard does fall for it, and their plan fails anyway. They have the drop on him, the home field advantage, superior numbers, a more advanced ship, the guidance of a Reaper, and they still can't kill him, thus establishing themselves as bumbling fools. Worse, they didn't even need to beat him in a gunfight. They could just have flown off with him and left the Normandy behind.