I loved the GameCube... because... well... it was the only console I had during that generation. I played a ton of games on it and still have it on hand to boot up SSX 3, Spider-Man 2, Soul Calibur 2.... Apparently I was the only one who bought third-party games for the GameCube. With the GameCube helping Nintendo secure third place (out of three?) in the last hardware generation, I doubt you could call it a success. Of course, that doesn't mean Nintendo wasn't planning on learning from their mistakes.
Speaking with investors, Nintendo CEO Satoru Iwata has stated that one reason the company decided to drop the price of the Nintendo 3DS was thanks to lessons learned from the GameCube. The company's management feel that the GameCube represents a huge missed opportunity, with moves not made to utilize the hardware in the fullest.