I do not for the life of me know why GC generation people insist the GC controller was so great.
It was okay. But the L/R buttons were TOO goddamn stiff, the d-pad was laughably microscopic, being practically useless to use in actual games, the placement of the "z-trigger" was awful, and in general, it just wasn't that great. Functionally, and comfort-wise, the N64 controller, in spite of it's silly shape and huge size, was far better. The SNES controller is still pretty much the best all-around controller they've ever made, and the GamePad, in all honesty, is the best controller they've come up with since the SNES. Why? Because, it has a large, comfortable d-pad, nice button placement, big, comfortable L/R buttons, a huge touchscreen that makes many things so much better than motion controller (or using the d-pad/analog + buttons to type in web browsers, etc., and even though motion controls were a passing fad, it DOES still also have the most advanced motion sensing, I do believe, on the market (thanks to the nine-axis).
But yeah. SNES controller rules. GC controller really had too many issues to be considered as "great" as so many seem to think it is, IMO.