Huh. You know, I was looking through my old top 50 list, and it turns out I have a lot more OG Xbox games on there than 360 games.
Halo: Combat Evolved
Half-Life 2
Psychonauts
Beyond Good & Evil
Halo 2
Far Cry Instincts
The Elder Scrolls III: Morrowind
vs.
BioShock
Gears of War
Xbox 360 definitely had the bigger and deeper library but I'd argue OG Xbox had the best top-shelf games.