http://www5e.biglobe.ne.jp/~hokora/english/index.html

This place has sales stats of the top 50/100/whatever titles for PS2, Gamecube, Xbox, Gameboy Advance, and even N64, Dreamcast, and Wonderswan (yeah, FF1 fans know about this system ).

If you've ever been questioning how software sales have been going for any of the current-gen systems, here's where to find out

Notice- PS2 stomps all over everyone, GC pwns Xbox (especially in Japan), etc... though this doesn't include hardware sales, where it goes PS2 > Xbox > GC, I believe.