Jade Empire is my favorite game of all time by a wide margin. Wonderful setting, characters, and story, if only it weren't so short.
Deathrow is an underrated classic as far as futuristic sports games go.
Fable the Lost Chapters, despite all it's flaws, is to me the best game in the Fable series.
Hulk Ultimate Destruction is a fun sandbox game that a lot of people missed due to it being a Hulk game.
If you haven't played them on the PC or already bought them Knights of the Old Republic 1 & 2 are both very good RPG's.
If you missed getting it on the PC Morrowind Game of the Year Eddition is an amazing open world game. Yeah it's probably better on the PC, but I didn't have any trouble pouring hundreds of hours into the console version.