Keep in mind that software sells hardware and the Gamecube had games readily available for players to enjoy. Right off the bat there was Super Mario Sunshine, Mario Kart DD, Windwaker, and Smash Bros. There wasn't a 2-3 year wait for those titles.(guestimating).
They also inherited the leftovers from the Dreamcast to add to their library. Wii U only has a few NEW great games right now: Super Mario 3D World, Pikmin 3, Sonic Lost World, and Maybe New Super Mario Bros U. other than that, the console's hardware consists of remakes, crappy Wii motion games, and oddballs everywhere. If we are to predict that the Gamecube will outsell the Wii U can we at least wait for Mario Kart, Zelda, and Smash to do what ever damage that they are capable of?







