Just imagine all the meltdowns!

No single game will do it, but a load of unique and appealing exclusives to Wii U would.
That doesn't mean Nintendo buying up 3rd party exclusivity, assuming major players in the gaming market can be bought like that, selling exclusivity can have a damaging effect to their reputation and the big guns won't do that unless it does something more than just gets them a load of money, they need it to have a positive effect on their overall public image.

More like Nintendo either needs to develop games internally, building new studios, using existing Nintendo owned devs to make new games or they partner up with lesser known external studios that have yet to make a name for themselves, because that will be way more appealing to the overall games community, it basically shows that Nintendo really cares about giving something back.

In order to get 3rd party, Nintendo should have built a system that is seen as a viable option to sell a good chunk of those publisher's games.
Exclusivity of 3rd party games isn't needed to get huge hardware sales from 3rd party games, you just need to have the most appealing platform for those titles as far as the 3rd party audience is concerned.

The best thing Nintendo can do is focus on making a big, compelling and quality library, using their existing library of IPs and making new ones, that provides an equal level of variety as Playstation (I always say Sony's variety is why they have been as successful in gamers eyes all these years) and quality that appeals to every kind of gamer.
Focus on one element in the market and neglecting any of the others will always lose you millions of potential customers.

Go back and read what I said again, because I didn't say anything about Watch_Dogs trailer graphics happening on the Wii U. And I'm not talking about general quality issues... in fact, I wasn't even suggesting that the Wii U version would resemble the other ones so that improvements would apply across the board. I was talking about a distinct Watch_Dogs game, with gameplay and style specific to the Wii U version. Note the wording of my comment: "living up to the gameplay of the trailer". Not "duplicating the gameplay of the trailer" or "duplicating the gameplay of the other version at the quality of the trailer".

Everybody, and I mean everybody, who saw that first trailer could immediately see the potential for that gameplay to be fit to the Wii U in a way that wouldn't work on any of the other home consoles.

I would prefer a Final Fantasy VII remake, but obviously GTA VI would make the WII U sell much better.
I think that a Star Wars exclusive or a Pokemon MMORPG would also boost the sales very much.

I 100% agree that one single game could never save a console.

I also agree with the fact that Nintendo really needs to focus more on 2nd party and in house devolpment. Nintendo has a ton of resources and connections at their disposal that come from being a company for over 100 years. Its time to take full advantage of that. Up until this year, Nintendo hasn't turned a profit in a while. Now that they are I personally think its time to dip into that vault of cash and start rebuilding/expanding your empire. Go big or go home basically. Amiibo, handhelds, and new IPs are the way of the future for sure, but Nintendo already does certin games and things so well, that they also cant give up on that aspect of things. 

A more powerful console isnt always the answer for attracting 3rd parties. Honestly it comes down to money. Tons of indie companies code for so many platforms that range from cellphones to supercomputers so that isn't exactly the issue. 3rd party games have traditionally sold poorly on Nintendo platforms since the GCN days. Maybe eariler. Thats up to us fans to change. Also a lot of 3rd parties do not like Nintendo because of some seriously shady business practices in the 80's and 90's. 

A massive library of quality, compelling titles certinly would help. I personally love Sony, not as much as Nintendo, but still the love is there. As it stands this generation, no company is really embracing a huge library. If you exclude digital indie offerings and focus solely on physical offerings, Nintendo blows them all pretty much out of the park. I think part of the issue is Nintendo perception. If you don't believe me, look at how small the Wii U's section at Gamestop is the next time you go in. Honestly, it makes me sad :

What do I prefer? A Metroid title that pushes story in a well written way. I would love to see the quality of writing rival that of Mass Effect. We need something to wash away the bastardisation of the series that was Other M, treating Samus with no respect and turning her into more of dense Megan Fox like character rather than the smart and capable bounty hunter she should be.

What would actually help? Ocarina of Time HD done in the Wii U tech demo style.

Final Fantasy VII

Not that I like the game much, but it appearing on Nintendo would right a historical wrong.

you already know that those games in PS4 and XBOX One are 85% similar games right which 3rd party developers have created annually - COD, GTA, BF, AC, Sports games.  Plus  FF, DA:I, SM etc....    Those would sell a lot.... 

so Nintendo should still have those IPs someway or another. and add more value.  It is always like this since GCN i believe, Nintendo have ton of quality IPs published or developed by Nintendo but they aren't getting the 3rd party blockbuster ones.

They need the FF to be back in Nintendo.  They need to get a slice of those GTA, COD, BF, AC etc... and be part of it annually.... Exclusive 1st party = it is always Nintendo.... but 3rd parties ain't coming so Nintendo should do something about it.  

Co-developed with 2nd parties might help but still we need to those blockbuster IPs. 

Maybe a 2D Mario, a 3D Mario, Mario Kart or Smash Bros. game. Wait, all of those have already been released? Uh-oh.

See bolded comment.