I own an Xbox but have played less than 5 games on it (I won it for free), and had a PS2 for about 6 months but my bro took it when he moved out. I'll say that Halo is my favorite 'Box game though and Katamari Damacy is my favorite PS2 game.
Cube:
1. Metroid Prime
2. Resident Evil 4
3. Pikmin
4. Super Smash Bros Melee
5. Windwaker or Paper Mario