Looking at the top 25 or so best games from each platform (minus old ports and sports/mini-game-a-thons):
GameCube: Metroid Prime, Resident Evil 4, Zelda: Twilight Princess, Zelda: Wind Waker, Super Mario Sunshine, Metroid Prime 2, Super Smash Bros. Melee, Pikmin, Pikmin 2, Soul Calibur II, Viewtiful Joe, Eternal Darkness, Metal Gear Solid: Twin Snakes, F-Zero GX, Animal Crossing, Prince of Persia: Sands of Time, Beyond Good & Evil, Resident Evil 0, Star Wars: Rogue Squadron II, Star Wars: Rogue Squadron III, Paper Mario: TYD, Mario Kart: Double Dash, Viewtiful Joe 2, Tales of Symphonia, Fire Emblem: Path of Radiance, TimeSplitters, Final Fantasy: CC, Wave Race: BS, Resident Evil REMake, DK: Jungle Beat, Super Monkey Ball.
Wii: Super Mario Galaxy, Super Mario Galaxy 2, Mario Kart Wii, Super Smash Bros. Brawl, Metroid Prime III, Zelda: Twilight Princess, Zelda: Skyward Sword, Xenoblade, NSMBU, Kirby Epic Yarn, Donkey Kong Country Returns, Little King Story, Sin & Punishment 2, Monster Hunter Tri, GoldenEye, Punch-Out!, Tatsuonko Vs. Capcom, Murumasa, The Last Story, Fire Emblem: Radiant Dawn, Super Paper Mario, Excite Truck, Kirby Dream Land, World of Goo, Rayman Origins, Kirby: Return to Dreamland, Red Steel 2.
N64: Super Mario 64, GoldenEye, Zelda: OoT, Zelda: MM, Perfect Dark, Conker's Bad Fur Day, Banjo-Kazooie, Banjo-Tooie, Turok 2, Beetle Adventure Racing, Star Fox 64, Kirby 64, Wave Race 64, Star Wars: Rogue Squadron, Star Wars Episode I Racer, Mario Tennis, Mario Kart 64, Blast Corps, Donkey Kong 64, Jet Force Gemini, Killer Instinct Gold, Excitebike 64, San Fransico Rush, Ogre Battle 64, Diddy Kong Racing, Paper Mario, F-Zero X, Pilotwings 64, Super Smash Bros.
SNES: Super Mario World, Final Fantasy VI, Super Metroid, Legend of Zelda: LttP, Star Fox, Yoshi's Island, DKC, DKC2, DKC3, Super Mario Kart, Chrono Trigger, Earthbound, Contra III, Street Fighter II Turbo, Mortal Kombat 2, Earthbound, Castlevania IV, Sim City, F-Zero, Pilotwings, Secret of Mana, Megaman X, Super Punch-Out!, Tetris Attack, Super Star Wars, Super Empire, Super Return of the Jedi, Mario RPG, Earthworm Jim, Super Mario All-Stars.
I'd say Super NES is the best, then there is a fair drop off, but GameCube is probably underrated in actual software quality. Mario Sunshine not being that great really is what sinks the GCN a bit, if Mario Galaxy was a GCN game, it'd be far better remembered, in terms of depth, GCN had a lot of good games and good variety. Shame they made it look like a damn console for an 8 year old and that basically killed it right from the get go.
Squaresoft did great work on the SNES, Rare did a lot of heavy lifting on N64, EAD Tokyo saves the Wii IMO.