I'll say the Playstation controller, since, well...It's been pretty damn awesome for like...a decade. Seriously, look at them. The only thing that has really changed is the vibration function, smoothness of the analog sticks and buttons, and wireless capability. Oh, and they saved a bit of material off the bottom of the shoulders, so that you only really have to press down on the L/R2 buttons, instead of pressing them in. Which is, actually, rather nice.
Oh, and the gamecube controller was awesome, except for its tendency to have a pull on the stick that made you drift.