Lets see, Nintendo's target audience with Wii was the causal gamer and non-gamer. The touch screen controller is actually a complex setup as the controller is large and requires attention to different screens (which aren't adjacent like with 3ds). This is in contrast to many games on Wii which used one or no button.
Second, the hardware is not high end, but the launch price of the console was highest for Nintendo console. I get that the cost is coming from the controller (which is higher end than the Xbone or PS4 controller), but I don't think it is a selling point as per my last point.
So we have a complex console aimed at casual and non-gamers, with low end hardware at a premium price. It is simply a product without a market.
That and Nintendo's games haven't been great yet. Nintendo is still among the best, but they haven't produced a game you would claim to be the most impactful game of the generation. They have with every previous console other than Gamecube (Mario, Donkey Kong, Zelda, Pokemon, Wii Sports, etc.)
Lifetime Sales Prediction - 6/29/2013
Wii U - 38 million
XBOX One - 88 million
Playstation 4 - 145 million
