I really like the Gamecube controller... The only thing about it that could arguably be bad is the Z-button... It really is the only flaw in the design i.m.o.
Furthermore, I would agree with the fact that the controller isn't as well suited for FPS-games as it's competitors back in the day. But well, Gamecube didn't get that much to be bothersome.
It's also the only console of which I have purchased 4 controllers! It's a pitty Nintendo stopped producing Wavebirds, since demand is still high because of VC and optional GC-controller use in the latest hit-entries from Nintendo's biggest franchises.
And if one would ask... PS2/Xbox/GC controller; GC>>>PS2>>>Xbox, controller-wise.