The GameCube had Smash Bros. and Super Mario and Zelda and Mario Kart and Pikmin and Resident Evil too.
The reason the Wii sold so much more is because the Wii appealed to more than just Nintendo fans because of Wii Sports/Wii Fit and then the nostalgia of people wanting to play 2D Mario again like they did in the 80s.
But IMO both of those wells have dried up for Nintendo. Casuals have moved on to smartphones and tablets and aren't coming back now that they're used to getting arcade type gaming fixes for 99 cents a pop that fit into their life style better than a dedicated home game console they have to spend $300 for.
What hardcore gamers don't understand is casuals don't want to sit down and play games for hours and hours on end. The have sweet tooth for gaming once in a while, but that's something a short 10-20 minutes a day (if that) can be satisfied by cheapo smartphone or tablet devices, which are more convienant anyway, because you can play them on the bus/train, during the lunch break, in any room of the house, etc.
The vast majority of Wii users did not purchase or care for Zelda or Smash Bros or 3D Mario.
And the appeal of 2D Mario is normalizing because it was special when NSMB1/Wii came out as many people hadn't played a 2D Mario in like 10+ years, but it's not a big deal anymore when you already played the last 2D Mario just 2-3 years ago.
