It's stupid. As I have pointed out many, many times before, BioShock is what I'd like to call a "flawed masterpiece" in that it has all the makings of an instant classic, but falls short in so many ways that it's hard for me to call it something of the sort. The ideas being presented in BioShock 2 are interesting, and the quality and execution of the game itself looks good (though never trust a trailer, obviously).
The problem is that BioShock 2 is a completely unnecessary game. The entire thing screams of a forced effort, one made not out of respect for the original but out of a desire for profit and for creating a franchise that can be drawn upon time and time again. The original BioShock, for all its weaknesses, has one very strong positive: it is an entirely self-contained experience. Most games set themselves up for sequels, have stories that never end or end poorly and with too many loose ends, have worlds that demand to be explained and explored more. BioShock, though, that game is entirely its own thing. We've seen all we need to of Rapture; the story has a beginning, middle and end that we witness within the game; the characters finish their business. There are no real loose ends, there are no unsolved puzzles, there are no deep dark hidden secrets waiting to be uncovered.
And so, when BioShock 2 tries to add on to what is already a whole piece, it can't help but looking like a third wheel or a second fiddle. Big Sister? Ugh. More mutated and messed-up Splicers? Oh boy. More of Rapture to see? Whoopee. All the familiar characters are back, despite having no compelling reason to be? Super. Brand new powers to utilise, despite no compelling narrative reason for them to exist? Sounds right.
Well, at least it's not as bad as it could be. Maybe they're saving the Little Brothers for BioShock 3.