Forgetting about the games on the systems, we should compare....
XBOX has a built in 8 gig harddrive. You can save games on it, save pieces of a game to decrease load times (something the PS2 has problems with), download new maps or game items, and alot of games allow you to play your own music from the harddrive during the game. I don't remember all the details, but I do remember that the XBOX has the most advanced hardware.
For the most part, the ps2 comes in second hardware wise. Then gamecube.
Also, from what I have heard, XBOX Live beats the other online console play....oh wait a minute...
Then if you do take the games into consideration:
XBOX: Halo, Blinx, Splinter Cell
PS2: GTA 3/Vice City, Metal Gear Solid: something, Hitman 2
Gamecube: Metroid Prime(the only game worth buying on gamecube imo)Those mario games, Smash Bros, there are probably others...
I say Blinx because it is a platform jumper, your mario type game. Basicly, to me it seems like XBOX is the way to go.
Edit: Here http://www.planetxbox.com/hardware/system/
That might be biased, so someone else post another link from somewhere else.