Perhaps not equal to Bioshock, but a worthy sequel nonetheless.
Bioshock 1 and 2 build characters and backstories so well that you actually feel like you have a place in the world and attachements to the characters; something that is very hard to achieve in a video game.
Bioshock 2 was fantastic, but with the exception of its final act, lacked the grandeur, novelty and polish of its predecessor.