[Uchiha Sasuke]

I own all three and i say go for the xbox now.It has a really nice selection of some good games out right now.Gamecube does have some awesome titles but theres not enough of them.Go get the xbox first.

Gamecube:

SSBM
RE
Pikmin
Sega Soccer Slam
Wave Race
Star wars Rouge Leader


Those are the best ones i played on GC so far

Xbox

Halo
Hunter the reckoning
Elder Scrolls Morrowind
Outlaw Golf
Blood Wake
Wreckless
World Series Baseball
Ralli Sport challenge

but of course these are the some of the good games out now.The future lineups are very impressive for each console