I've noticed a bit of a pattern. N64 fans tend to consider the Gamecube a disappointment, but people who didn't like N64 tend to consider the Gamecube a big improvement (although not a panacea).
Gamecube may have a number of games that are inferior to their N64 counterparts. Mario, Mario Kart, 1080, Star Fox, Zelda, and so on. But, it has a bunch of good games for which there is no N64 counterpart. Super Monkey Ball, Pikmin, Viewtiful Joe, Tales of Symphonia, Chibi-Robo, Skies of Arcadia Legends, Lost Kingdoms, Alien Hominid, Beach Spikers, Baten Kaitos, Killer 7, and so on. N64 fans focus on the former. I prefer to focus on the latter.