BackFire
Blood. It's nature's lube
Going to the game of the year Bioshock vs Halo 3 argument.
Bioshock is a much much better single player game. Its pacing and story both wipe the floor with Halo 3. Halo 3 started off really strong as far as pacing goes, in fact, the first 7 levels were great, I think. But it lost a lot of its momentum towards the end with repetitive levels and just rehashing things they did in the prior games in the series. Bioshock's excellent pacing and story never faltered, it stayed strong the whole way through. And the story was much more engaging, emotional and well thought out than Halo 3's.
Also the atmosphere and level design are much more complex and effective in Bioshock. Despite Halo 3 having the best level design in any of the Halo games, it did, at parts, feel like it was just going through the motions (Okay, time for a vehicle segment, okay, time for a flood level, okay, time for an indoor environment). The whole world of Bioshock felt organic and never once broke the suspension of disbelief by taking an easy way out. The each level felt cohesive to the next, and made the world feel complete and together.
Now if you want to take into account multiplayer, obviously that's another can of worms. My personal vote for game of the year so far is Bioshock, because the single player portion of both games are the most important. Bungie has said from the get-go that the Campaign was their main focus for Halo 3, so comparing each games single player aspect, Bioshock wins, I think.