1. Ninja Gaiden Black
2. Jet Set Radio Future
3. Psychonauts
I didn't play a whole lot of original Xbox games, but I guess my top 3 would be in no real order:
Pac-Man World 2
Tony Hawk's Underground
Star Wars Episode III
That last one is not a joke, I loved the game so much I remember coming home and just beating the final level over and over just because it was fun.