Bioshock is a game that mixes the best of First Person Shooters and Role Playing games, and will tell you by the end if you are Mother Theresa or Spencer Pratt (IE, useless douchebag)
Bioshock starts in an airplane and winds up under water. You go to Rapture, an underwater city built on the principles of Ayn Rand's Objectivist philosophy, and shows how fucking nutty people go when they get to do whatever the hell they feel like doing.
By the time you show up, the whole ecity is falling apart and is run by a crazy asshole named Andrew Ryan. Ryan originally concieved Rapture as a place where people could live out their full potential without having to worry about morality and other minor shit like that. When people turn out to be fuck ups because, well, they are people, Ryan loses his shit. By the time you arrive, so has everyone else.