GameCube first party is overrated.
Mario 3D World >>> Sunshine.
Like seriously take off the nostalgia glasses with Sunshine, it's a terrible Mario game with bloated level design all set on a tropical island (who the hell thought a Mario game with all tropical themed levels was a good idea?), that had camera glitches and bugs up the wazoo and the back end of the game was piss poor.
Splatoon >>> Pikmin
These were the so-called "new IP" of the GameCube ... I'm sorry, Splatoon is way better. It's a far better game and truly the next great Nintendo IP. Not only that but Wii U has Pikmin 3 as well.
Mario Kart 8 >>> Mario Kart: Double Dash
Double Dash had a pathetic number of tracks, MK8 has far more content.
Smash U = Smash Melee
Smash Melee was the one big IP Nintendo got right on the GCN, but Smash U matches it IMO.
DKC: Tropical Freeze > DK: Jungle Beat
EAD Tokyo made a good effort here, but a "real" DKC game with actual controls the return of David Wise trumps a spin-off DK game with bongo controls.
If Zelda U is better than Wind Waker, then the Wii U has the GameCube beat in many major Nintendo IP.