Now imagine the Wii U sales if it had The Legend of Zelda, Mario Kart, Mario Party, Super Smash Bros., a Super Mario Galaxy sequel and were $150 cheaper.
It wouldn't be at Wii levels, but the now stronger Nintendo franchises (especially considering it wouldn't be a "Sunshine" Mario or "Wind Waker" Zelda) would easily put it above Gamecube levels.
The Gamecube/Wii U comparison remains invalid.