For me, co-op gaming offers some of the most fun you can have on an Xbox 360. While a title like Call of Duty 4 can offer an excellent single person, campaign experience, opening the game play up to co-op/multiplayer can make it shine, especially when the developers put considerable thought into the elements of team play and cooperation for in-game tasks or puzzle solving. It also adds a social element to the game, which is what play is really all about anyway.
