Battlefield - never played, but it's the talk of the town: rated 9.5
Little Big Planet - Awesome game. Totally worth it.
Rock Band - pricey, but awesome for parties.
Really, Call of Duty is all you need. WARNING: It is like Crack. Only play online. Don't waste your time playing offline.
If this doesn't float your boat, here is the best website for game ratings:
http://www.gamespot.com/
http://www.gamespot.com/games.html?type=top_rated&platform=1028&mode=top&page_type=games&tag=subnav;top_games