In terms of game controllers used in fighting games, the order would be...
PS2/3, Xbox, GC.
The problem with the GC is the layout of the input buttons. On top of that, there are a total of 7 buttons as opposed to the PS which has 8 buttons. Low kick, medium kick, high kick, triple kick, and the same for punches. The buttons on the front of the controller are in different shapes and sizes, and don't have an exact "pattern" as opposed to a PS controller which is 4 same sized buttons in a diamond shape. The trigger buttons are easy to access, and have a consistent size as well. The GC trigger buttons are fine, but the Z button is smaller and harder to press. Then the D-pad isn't no where near as good as the PS.
Overall, stringing together combos, commands, etc are more difficult on the GC.