Because Just Dance and Carinval Games and Mario & Sonic Olympics aren't "great" games by any metric. 

Well sales can also be an aribiter too. If the PS3 didn't have great games, there's no way it would have overcome that terrible start to eventually sell 90+ million consoles. 

With Wii, if the casual games that Nintendo was banking on were truly substantive experiences rather than fads, then things like Wii Sports and Wii Fit should still be relevenat today the way GTA is, but they're not. 

There's also the simple matter of craftsmanship ... I don't have to like a game to acknowledge it's well made. 

Worst time was 2005

I did and there's 6 or 7 on the Wii that are really, really good. 

I think you'd have to do a lot of mental gymnastics to claim things like Mario Party, Super Paper Mario, etc. are belong in the "great" category. 

It's mostly the two Galaxy games, then a gap, then Prime 3, the two Zelda games (though they have quite a few problems), and maybe DKCR that I'd say are really great titles. 

The Wii U is already approaching that number, IMO by year end it may match it depending on how Star Fox and Mario Maker come out. 

You left out Xenoblade Chronicles.  Smash was a great game, even if not the greatest Smash.  

I don't believe that sales = quality either. Twilight and Justin Beiber are popular, doesn't mean they're any good.

And craftsmanship is worthless to me if it doesn't produce an enjoyable end result.

Star Fox doesn't have the greatest graphics, but then again I think a lot of people are ignoring that it's rendering two seperate frames at 60 fps in HD. 

The playable impressions from the show floor of the game have been positive, and the reason why I think it will be a good game is because it's the first Star Fox game in 20 years that has central involvement from Miyamoto and EAD. And the co-developer, Platinum Games isn't too shabby either. 

As for GTA ... look, the critical response to it, the franchise longevity as well. It's one thing to say "yeah but Twilight and Justin Bieber are popular too, lulz", but they won't be in 5 years because they're flash in the pan fads. GTA has been going strong for over 12+ years now. The scope of the game pretty much dwarfs any open world game too. 

If it's such a terrible game, why is it pretty much the one IP that Nintendo fans beg for most when asking for third party IP as well? 

Some of the repsonses to E3 are overblown, it's mainly Metroid/Zelda fans that are upset, this holiday season Yoshi's Wooly World, Fatal Frame V, Super Mario Maker, Xenoblade X, and Star Fox Zero are launching between September-end of December it looks like. Maybe Mario Tennis as well.

That's better than any of the Wii's holiday season release periods. 

2010. Donkey Kong Country Returns, Goldeneye 007, Kirby's Epic Yarn, Sonic Colours, Epic MIckey, Call of Duty Black Ops.

I like the Wii U list better, two games from EAD, versus none in that holiday season. Also BLOPS on Wii ... eh .... 

Still for all the crap the Wii U is taking is actually does have a very solid holiday lineup better than most Wii holiday periods. 

Relatively to the Wii it's doing OK I would say. If Nintendo hadn't been completely unreasonable and made a machine that would allow for some easier PS4/X1 ports, this wouldn't even be a contest. 

Thing is, while Wii didn't have the best third party support, it was still better than Wii U's.

In 2010, it got Goldeneye 007, Sonic Colours, Tatsunoko vs Capcom, Red Steel 2, No More Heroes 2, Epic Mickey, Black Ops, Sonic All Stars Racing, Prince of Persia, Sky Crawlers, Need for Speed Hot Pursuit...

Again, not a AAA extravaganza, but more than Wii U currently has.