Sorry, but as blasphemous as this sound to the users who say otherwise, I rank the GameCube above the Nintendo 64 as well.
The 3rd party support the GameCube received was CONSIDERABLY better than the N64, whose 3rd party support dried up after 1998. Outside of Star Wars and the WWF/WCW games, what else was there? Meanwhile, the GameCube, which also got Star Wars and wrestling games, had Sonic Adventure 1 & 2, Sonic Heroes, Resident Evil 4, and Tales of Symphonia, all of which were on par or better than the Rare games on the N64. The GameCube was the system that saw Nintendo start repairing a lot of the burned bridges and damaged 3rd party relationships they had with the Nintendo 64, and to a lesser degree, the Super Nintendo. They started cutting back on a lot of their BS and started making a conscious effort to involve 3rd party companies and meet them somewhere in the middle.
As for the First party games. The GameCube introduced some of Nintendo's now bigger and more prominent franchises: Luigi's Mansion, Metroid Prime. It was also the introduction of Animal Crossing outside of Japan because the N64 version was never released overseas. There's also Pikmin.
Furthermore, some franchises that were absent on the Nintendo 64 made their comebacks on the GameCube: Metroid, Fire Emblem (consoles/first Western console release), Final Fantasy (While it only had Crystal Chronicles, it's better than what the N64 got - nothing.), Metal Gear (The Twin Snakes is better than nothing at all.)
Almost every major or signficant A & B tier Nintendo franchise you can think of got a game on the GameCube: You had Mario in just about every franchise/genre he covers, Zelda, both 2D and 3D, Smash Bros., Metroid, Pokemon (that wasn't the mainline handheld games), Fire Emblem, Star Fox, F-Zero, Pikmin, Animal Crossing, Kirby, Donkey Kong (sort of), Eternal Darkness, and Wave Race. All that's missing is Earthbound, Kid Icarus, Yoshi, Splatoon, and Xenoblade. The former two weren't on the N64 either, and the latter two didn't exist yet. The GameCube was the last time Nintendo really tried to give all of their franchises attention and success before they started leaning too heavily on the Wii series, Mario, Pokemon, and Zelda. Since then some of the lesser ones went into hiatus for a long time like Pikmin and Star Fox or just straight up died like F-Zero and Wave Race.
It's a case of quantity over quality. But, there was most definitely quality, some of which was better than what preceded it on the N64.
Melee >> Smash 64
Double Dash > Mario Kart 64
F-Zero GX > F-Zero X
Mary Parties 4, 5, 6, & 7 > 1, 2, & 3
Thousand Year Door > Paper Mario
And what will probably be the most blasphemous thing I say on this post:
Super Mario Sunshine > Super Mario 64
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