The X Box really doesn't have a lot of quality games yet. Nothing's hit its full potential.
And Sony did fuck up the PS2 pretty badly. It actually has more power than a GameCube in it, but the circuitry inside creates a bottleneck due to one CPU controlling it all. Nintendo got around this by using a few sub-CPUs (but the total power is still less than a PS2) to divide the load and the results do show.