Xbox 360 Game Suggestion

Hey everyone...Well, this year for xmas, I could finally afford to buy my boyfriend an Xbox! :) I'm excited, he's wanted one for a long time...unfortunately, I have no idea what would be a good game(s) to go along with it. It's not that I don't know what kind of games he likes (Gears of War, Resident Evil, BioShock, Far Cry), it's that a lot of these games, he'll play his computer. And I would hate to get him a game that he's already played... so I'm just wondering if anyone can suggest one that is strictly for Xbox, or will be at least until after Christmas... haha.Any suggestions would be much appreciated...Thanks in advance!!!