3rd party support is important, but no, definetely it's not the key to WiiU success.
Since the N64, the best-selling games on Nintendo systems are always 1st-party games (with very, very, few exceptions like Just Dance, Sonic Racing Transformed, or Monster Hunter).
People will always buy Nintendo systems interested primarly on their exclusive content, and this content is almost always 1st-party or co-developed games.

Thank you. :)

I'm talking about real success, above cube numbers, and above and beyond Wii-craze success. Something tangible, that can last. If they did it with the NES, they can do it again.

Rayman Origins didn't do much if any better than PS360 on Wii, so I don't think Legends would have.

Sadly I think the damage is done, they took to long to rectify their problems.

If they don´t have or bring a game that is a game changer then they will struggle this whole gen.

If a game isn't exclusive, it's easy to conclude that's the reason it sold relatively less, not much more or on par.

Here's a counter-example from the 3DS, a timed exclusive:

There are others that show that a game can sell a lot better if/when exclusive than when it is a multiplat.

I think what you're trying to say is "why should devs make exclusives when they can make more money making them multiplat". The main reason is that the market on the twins is saturated. A developer could build its own market in the span of a generation or two on Nintendo platforms and have the chance of making Nintendo-like sales on the long-run, if they can pull it off.

I totally agree with the guy. Most of the games I want right now are third party exclusives like Monster Hunter Ultimate/Lego City and the upcoming Sonic and Xenoblade 2 games.

It's like Nintendo first party have done all they can avoid the WiiU like a plague in its first year.

W 101 may not pass 1M but bayonetta has more potencial, especially since it will release when wii u has a 10M+ installed base.

Wii was a real sucess. It´s now the 3rd best sold console of all time. It will be very hard for any other console in the future to beat it. But a success of a product is not directly related to its capacity to beat direct competition. It´s about making profits. If WiiU sells around 40-50 million in its lifetime, it will guarantee enough profits for Nintendo and will be considered a success.

And still, even on the Wii  1st-party titles were the best-sellers. Which games drove Wii sales ? Wii Sports, Wii Fit, New Super Mario Bros, Super Smash Bros Brawl, Wii Party, Zelda, all 1-st party; Just Dance is the only exception. On the NES era, Nintendo had a very arrogant approach that prevented developers to launch games for other platforms. They can´t do that this time, it´s a completely different scenario.

I do believe that it will do well on WiiU because WiiU players have been experiencing the game for quite some time, with the free Challenge App. Overall reaction was very good, despite the initial anger towards Ubisoft due to the delay.