Halo 2
Despite a rather short campaign and a disappointing storyline, Halo 2 is an exceptional shooter that frequently delivers thrilling, memorable, and unique moments in its online, co-op, and single-player modes.

Halo
Not only is this easily the best of the Xbox launch games, but it's easily one of the best shooters ever, on any platform.

Star Wars Battlefront II
This sequel to Star Wars Battlefront improves upon its predecessor with a variety of gameplay enhancements, such as upgraded AI, more than 16 new battlegrounds, and greater story emphasis. In addition to the rebel, clone, and droid warriors from the original game, you can play as a Jedi, complete with lightsaber attacks and force powers.