I'm sure it would've put a better fight against the Xbox One, but just barely on par in terms of sales.

I voted no. The Wii U failed because in the eyes of many, it's an undesirable product. It's a console that's doubled down on Japan while compromising on the needs of the global market. It's design is focused on exclusively on Japanese needs (small, low power consumption, Off-TV Play), while the Japanese gaming market has migrated mostly to mobile. Not to mention Nintendo's own problems with releasing software globally, physically, and consistently.

Nintendo's 3rd party woes are real, and are a real part of the Wii U's failure, but there's more to it than that. IMO, no conversation has found why the Wii U failed commercially because the Wii U's problems are fractal. You don't go from 100m to ~15m without some fundamental rot in the core idea. Michael Pacter said that the Wii U, in his words, was "a crappy product." I disagree, I don't own one, but my cousin does. I think it's a well built, well engineered product that does what it does very well; it's just that no-one cares about what it does, they all want PS4s and XB1s.

I am a PlayStation gamer nowadays but in my childhood and teen years I was a huge Nintendo fan. I had all the itinerations of the Gameboy but when it came to the DS I lost interest in favour of PlayStation and essentially Grand Theft Auto.

Now the above statement is important in answering your question in that Nintendo catered to my need for video games i could sink 100s of hours and still be wanting more, but I reached a point where I needed something more engaging and in essence provocative than what Nintendo had to offer. Now lets say the Wii U had even specs with the PS4 (otherwise with current specs it simply cant recieve third party support) it still would not receive full third party support due.

This is because GTA V would not be allowed to be published on the Wii U and im doubtful as to Fallout 4 as well, but not only would the Wii U miss out on the biggest selling game so far but the utter primitive nature of its online capabilities would hinder it to such a point where games such as GTA V and Battlefield would just not be worth playing. Now there is no denying that the Wii U is a complete commercial disaster but even if it had solid third party support and better specs and even a decent online platform it would still not be anywhere near the PS4 as people no longer play Nintendo consoles for games like GTA or MGS they play it for Mario and Splatoon.

To the mainstream Nintendo has become stale and out of ideas and coupled with the excellent launch of the PS4 and Microsoft's valiant comeback there is just no place in the market for Nintendo to compete with them hence why we are seeing rumours of a portable NX and mobile Pokemon games now in order to expand their market and userbase.

Nah, but it would with XB1, for sure...

if nintendo had all third party support then there wouldnt be a reason really to buy the other consoles,unless you really like their exclusives or would be interesting in the 'slight' graphical upgrade for games

Nintendo cant compete with Playstation. Period.

The Gamecube had decent third party support and look how that turned out.

The Wii U might have done a little better, but it still would have undersold.

Lol. That's pretty laughable. The ol' "Sony is God" mentality. 

The answer to this thread is no. At least that's my take. I've said it many times before that the lack of third party support is not Nintendo's problem. Their problem is one of perception. Or the idea in the gaming community that they aren't the hip thing as Sony is. Some of is warranted is some is nonsense. Since the N64 days they have been about 1st party and they deliver. Their 1st party games aren't for everyone thought. At this point the Wii U is well worth it to have but most won't buy one mostly because of this bad perception they have. Even if they had the sane third party games so would still say Nintendo is for kids or some hate excuse.

It would sell much better thats for sure, because without 3rd party console is mainly for Nintendo fans, you can bet that lots people would buy console if in same time they have games like Fifa, Minecraft, CoD, Witcher, GTA....and game like Mario Kart, Zelda, Donkey Kong, Mario 3D World, Smash Bros...again it couldn't compete with PS4 but it would be doing much better than Wii U currently.

Also, when we have new announcement or new trailer for some new game, there is no version for Wii U, so indirectly we are getting message that Wii U is dead and isn't part of this gen, thats one reason why Wii U consider buying mostly Nintendo fans.

3rd party isnt only Wii U problem, Nintendo had some terrible decisions with Wii U (terrible and misunderstood marketing with bad name, high price, bad launch titles, software droughts...) that leads to very bad sales and 3rd party abounding, but it is one of the biggest problems.