I honestly have no idea why people love it. The only thing I can rationalize, is that GC was their "first system", or so, and they are very nostalgic about it. Because otherwise, in all blunt honesty, it's the worst controller design Nintendo has ever come up with. Wiimote/Nunchuk was kind of silly, yes, but it was more comfortable.

GC controller was fine, and the Wavebird was very convenient. But it also just had so many design flaws, from the TINY (and stiff as fuck) d-pad, to the weird analog (and stiff as fuck) L and R "triggers", to the ridiculously placed and tiny Z button, to the odd button placement that was not conducive to most fighting games, to the comically small second analog, aka "C-Stick" (taking the place of the C buttons on the N64 controller).

All in all, I cannot fathom any actual, practical reason, other than them liking the shape and size, for people to try and claim it as "The best controller ever". Granted, opinion and taste are totally subjective. But I just can't see it. I don't HATE it at all, it's fine. But playing anything that required major d-pad or L/R trigger use, especially, was a pain in the ass. Or rather, fingers.

its not at all nostalgia

the Gamecube controller has a fantastic feel in the hand. its shaped great, has a wonderful layout for virtually all types of games, and really clean feeling analog sticks.

Literally there's a reason that people are still buying Gamecube controllers and adapters to use on newer iterations of Smash. 

I would debate that the newest controllers on PS4/XBox are actually a little over the top. I feel like the shape is ehh and that its not necessary at all to have multiple L/R triggers and the extra full dedicated analog stick

a lot of controllers (even today) do not really sit in the palm of the hand THAT comfortable. I've never really liked the feel of the Playstation dual shock controllers, and frankly they feel pretty similar today to how they felt in the PS2 era. Xbox controllers tend to be a little big too

The Gamecube controller just has a fantastic layout, is high quality, and has a nice simplistic button arrangement. I feel as if you could play literally ANY game today perfectly with that controller

20 buttons on a controller just is not necessary

and what says a lot is that I would argue the later released 'pro controllers', Wii U tablet, and other things, all are considerably worse

I will say that if you have a damaged Gamecube controller it would take away a lot of the obvious greatness. worn down c-sticks that have the rubber torn off are uncomfortable. so OP its possible your friends controller was worn and therefore not really giving you the fulll experience

the Gamecube controller actually (for all systems) has been emulated in a few ways so I find some of the naysayers comments strange. especially with third party accessories, so many controllers have emulated it because it has a great layout and is extremely comfortable to the hand

The problem with the Gamecube controller is that the C-stick and D-Pad are garbage. Can't fathom what Nintendo was thinking there.
Replace the right analogue with a clone of the left and make the D-Pad larger and less stiff, and it'd be amazing.

Everyone has different sized hands... I thought it was a bit small but not bad.  One of my favorites is the ol' duke from Xbox.

for Wireless just play with the wavebird the first realy Wireless controller for consolle and gamecube

It was a high quality controller, and ergonomically a pretty great one. Never the less I liked the DS2 more and remains arguably my favorite controller of all time.

An upgraded version of the GC controller could be amazing for the NX to have

I sure the hell don't love it. The controllers wear out way too quickly or break often and the button layout is impractical.

Nostalgia really. When the GCN was relevant, the majority of people would piss on the controller(figuratively) all the time. The Z-button sucked, the C-stick was gimped and useless, the D-pad was tiny and basically unusable, the face buttons were asymmetric etc.

I have replaced the C-stick with the gray GCN stick, works so much better. Also the Hori Gamecube controllers are better in EVERYWAY. Bigger face buttons, bigger start button, two Z-triggers and more comfortable to hold.