What's your pick, and why?

Knights of the Old Republic. It was an engrossing RPG, rich of adventure, some truly memorable plot twists and awesome partners (yeah, I'm even including the self-righteous Carth). It's in my opinion one of the greatest games ever made, and far surpasses anything else inside the Star Wars franchise.

The runner-up would be either Shenmue 2 or Halo 2.

Ninja gaiden black. The best NG by far with gorgeous colourful visuals,challenging gameplay and awesome bosses. Runners up would have to be Jet set radio future, Splinter cell chaos theory and Project gotham racing 2. Xbox also had other amazing racing games like Burnout 2 point of impact,Burnout 3 takedown, burnout 4 revenge, Moto GP, rallisport challenge 2 and toca 3. I used to spend dozens of hours playing those games.

Halo 2 FTW! 

Riddick, Crimson Skies, Ninja Gaiden Black, Serious Sam, etc..

Incredible system that deserves more (a lot more) respect.

Ninja gaiden or fable. I cant really decide.
Escape from butcher bay was also a great game.

Edit. Forgot Panzer Dragoon orta. Best on rails shooter ever.

Halo 2 for me.

Sudeki! Hmm. . . dejavu.

Morrowind GOTY

PC gaming but with the convience of a console.

So many to choose from!

I'll go with Halo, which owns titles for best shooter, best launch game, and best Xbox game. It represented a huge leap forward for the shooter genre and it's still awesome 15 years later.

Other contenders are Half-Life 2, Psychonauts, Halo 2, and Morrowind.