The Wii U is Nintendo's worst console since the Virtual Boy, and its worst TV-based console ever (aside from maybe some niche console that I've never heard of or pre-NES stuff). It has the worst library of games of any TV-based Nintendo console, and even if there are some high quality first party games, every other Nintendo console has also had high quality first party games as well as a much stronger variety of 3rd party games.
The lack of 3rd party support isn't just an isolated decision for devs to leave, it's Nintendo constantly prioritizing their own 1st party games at the cost and uninvolvement of 3rd party developers/publishers. They've been doing it for several generations, but this is the first generation where the install base is so low that developers don't have any justification to develop for the console.
That you're getting "The best version yet" of some franchises is an easy thing to say with a new console. Similarly, Madden '16 is definitely the best version of Madden if they're compared directly, but most fans adjust based on the time of the release and rank Madden '04/05/06 or Madden '93/94/95 or Madden '01 much higher when adjusted to their releases. Similarly, Super Mario 3D World is a great game, has the best graphics of any Mario game, and still has excellent gameplay, but Super Mario World and Mario 64 were revelations at their release and they're still hallmarks of gaming some 20 or 25 years after their release. 3D World will hold up as a great game in 25 years, but it won't have the same impact or be remembered as strongly as Super Mario World and Mario 64. Beyond 3D World, Smash and Mario Kart are great, but they're not going to be remembered as strongly as other releases in the series even if they are still very good games.
But, sadly, the complete dearth of content is what makes this Nintendo's weakest TV-based console. Even while the Wii languished with shovelware over the last few years of its release, those first 2 or 3 years were so strong with content -- even if non-traditional gaming content -- that the console was such a breath of fresh air. Because of the install base, 3rd parties still adapted content to the console even if they were vastly inferior versions of games, you still got fresh, new content. There is none of that on the Wii U from developers other than Nintendo or tightly-partnered 2nd parties. Sadly, we've entered a world where the prospect of high quality, landmark 3rd party games on a Nintendo console is so unrealistic fans have shifted their priority to think that you can only get Nintendo games on Nintendo consoles, and so 3rd party games don't matter. But for generations, some of the best 3rd party games were being released on Nintendo consoles. Goldeneye and Perfect Dark were considered (and still are occassionally) the best shooters/action games released that generation, Turok and Turok 2 were considered excellent, WWF No Mercy is sitll widely considered the best wrestling game ever, Rogue Squadron, and Resident Evil 4 were two excellent action games. The idea that a Nintendo console would debut the best wrestling game, the best shooters, the best action games, and the best survival horror games ... today ... is a ridiculous idea that nobody entertains.
