The problem wasn't just that Nintendo didn't have titles, but that what titles they had were the wrong ones. None of the Wii U's software has actually showcased the gamepad or been major blockbusters.
Compare with the Wii:
The Wii's big title was Twilight Princess. The Wii U's big titles were Mario World and Pikmin 3...which got delayed almost a year. There's almost no comparison: Mario and Pikmin are titles people who already have the console will get.
Moral of the story: Zelda sells consoles. Mario and Pikmin does not.
I look in the future and see X and Zelda Wii U hitting the market around the same time FF XV does....this is going to be one tight generation. I still think the Wii U will do well in two console entertainment centers, but there are some heartbreaking decisions in the pipe come 2014.
NSMB Wii has sold more copies than almost every console Zelda combined.
Zelda didn't sell the GameCube and Mario and GoldenEye sold the majority of N64s IMO.
For all the bruhaha about Twlight Princess, it was easily outsold on the Wii by things like Mario & Sonic Olympics and Mario Party 7.
Wii Sports is the Wii's big game, that sold the console.