Battlefield: Bad Company 2 is an awesome first person shooter for the XBOX360/PS3 and the OP is right. Besides being a fun game, the sound mixing they've done in this game is one of the best I've heard. The game really pushes your subwoofer and I know - I am an avid gamer. Use Audio Option: War Tapes in game and you'll know what I'm talking about.
People often talk about movies or music when demoing there system. But this one is one the good games out there that has excellent audio
I would also recommend these title for great audio:
Call of Duty: World at War
Bioshock 2
God of War 3 (at least from the demo I played)
