for me.. best graphics in order from best to worst
xbox
gamecube
ps2
which is obvious because its basically the reverse order of their arrivals (which allowed them more time to impliment their graphics)
still, as some have mentioned.. the systems power has to be harnessed properly for the best results.. I think soul calibur 2 was a good demonstration of the systems' power.. as it was by a reputable developer that most likely used all 3 to the best of their ability.