Better graphics do not make them better. Most of the XBox games really suck. Except Halo and Splinter Cell.
If you have to choose between the two, I'd go with PS2. The selection of games is great. I own a XBox and a Gamecube, trust me, the nintendo games are far more better.. Especially since Zelda : Wind Waker came out
My XBox seems to sit there and collect dust while the gamecube is always on.