I don't care what the game is, I only judge a game when it has it's full polish, out for me to play. it's just like people telling me Jesus has a beard. Actually, i'm not a big christian BUT I would only see it to believe it.
Bioshock though, I could see it being the greatest game ever. But like I said, I treat all my video games the same before they come out

Won't judge anything until I play it. But Bioshock is taking a whole different approach to first person shooter, i'm tired of the sleepy settings i've constantly played, it's time for a change! *picket signs*
But you might be saying,"Well the setting might change, but does it have good gameplay". Man, I would bet hundreds that the gameplay is satisfactory.
Maybe best FPS ever? There are games like Fable 2, AC, Mass Effect, etc.
Lets not forget Halo 3, but i'm rooting for Bioshock over that title. Any day.
Remember, it's our opinions. I might think Fable 2 is the best, you might think Mass Effect is the best. No one, not even the almighty Lord of Hellfire, can tell us whats the best. It's our decision.