Not every parents buy to kids console that kids wants, especially when we are talking about younger kids which parents don't want to play violent games.

Nintendo had 20 million-is Nintendo fan base only with GameCube and that because PS2 was most popular console of all times.

Yes, casual drove Wii to 100m, but parents that buying console to kids were always big part of Nintendo console buyers, even on Wii U.

My point is that with just different and better marketing and name, Wii U would be at least on pair with GC numbers, and with better launch titles and more affordable price, at least on pair with N64 numbers.

Well here's the thing with younger kids. The parent is just fine and dandy buying them the much cheaper 3DS in that case. 3DS has all/most of the Nintendo franchises a kid that young would care about. 

Or unfortunately for Nintendo, these days it's becoming increasingly more and more the cheap Android tablet with free games (take that $40 cartridges) or a hand-me-down iPad. 

By the time the kids really "need" a console they're already in that "I want to play what the older kids are playing" phase and that leads to them really gravitating towards the Sony or Microsoft brands. When I go to a store like a Best Buy, there's just as many kids around the PS4 or XB1 kiosks as there are around the Wii U one. Nintendo does not have any special sway amongst kids. 

The main problem the Wii U is facing is that the Wii's main audience were casual gamers and Nintendo fans. Sure, a lot of other gamers got one as well, but the SD graphics, lackluster online features and lack of AAA multiplatform titles combined with its relatively short lifespan meant that a huge amount of them turned to Sony and Microsoft well before the Wii U launched.

With the casual gamers gone, what's left is the core of the Nintendo fans.

Not enough was done to bring those customers back. If a console can't play COD, FIFA, Madden, Assassin's Creed, Battlefield, FarCry etc, then it simply won't be the first choice for a huge amount of gamers.

Relly!? Can parents play NSMBU, Mario 3D World, Mario Kart, Smash Bros, Donkey Kong, Yoshi...with they they kids together in same time on 3DS!? Also some parents have more than one kid. Wii U can be literally played by whole family in same time, 3DS can't do that except every person having own 3DS but again not a same, beacuse it totaly difrent experiance playing on TV and on handheld.

True, but people are still buying consoles for their kids, especially parents who grew up with Nintendo, and they cant all play same game together and have great time like on Nintendo console with Nintendo IPs.

Like I wrote, not every parents buy to kids console that kids wants, especially when we are talking about younger kids that parents don't want to play violent games.

The main problem of the Wii U is everything.

Bad marketing from the beginning, european marketing was just terrible.

Focus an a controller Nintendo themself havn't known what to do with for over two years.

Wrong games. Starting with more of the same in actually very unimpressive graphics, like NSMBU. Yes, Splatoon shows that people still want new IP's from Nintendo and that Nintendo can have fresh ideas. And Super MArio Maker at least shows what you can use the Gamepad for (though you wouldn't really need it for an editor).
Instead of focusing more on coregamers Nintendo stayed with casual and cute. Not cute doesn't mean violent and 'mature' though.

Wrong deals: I liked Zombi U and i love Bayonetta 2. But people just don't care for those two nor W101 or Devils Third. They'll probably care no more for a new Project Zero. Sad but true, for marketing a console, those are the wrong deals today.

Nintendo did way better with third party games for the 3DS.

Marketing really was a small problem. As others have stated most of my friends thought it was a cool console but nothing really made anyone I know want to buy it until more recently and plenty more still have no desire for the console at the price it still is. Most people that came into my Gamestop had no idea that the WiiU existed until we talked it up to them. Even after that few wanted it due to its price compared to the 360/PS3/Wii. I love the WiiU but barely play it compared to my Xbone. I think the more core gamers would have been more apt to purchase it had Nintendo released a Zelda, Metroid, Mario(64,Galaxy,Sunshine type) or even the Starfox game with it. The casuals and parents would have been more likely to purchase it had it been cheaper...If Nintendo gives it a 199.99 price this holiday with bundled games I think they could get a lot more people on board.

Not only that if we go by that adage of "software sells hardware", then what casual gaming hit has Nintendo even made in the last 8 years?

Wii Sports and Wii Fit were huge hits of course. But that was 2006 and 2008.  Since then? Wii Music ... under performed. Nintendo Land? Disappointing sales could not carry the Wii U even for a few months.

Wii Party? Did well, but basically retreading the same territory as Mario Party/Wii Sports. If you look at the new casual gaming brands that have become break out new IP hits/household names, a pattern becomes very obvious ...

Angry Birds.

Boom Beach.

Candy Crush.

Farmville.

Fruit Ninja.

Minecraft.

Words With Friends.

Just Dance.

If we look at the new casual gaming breakout blockbuster hits since 2008/9 ... the vast majority of them are for smart devices. Coincidence? No. Just Dance was a late cycle hit for the Wii, but it does nothing for the Wii U. Why buy a Wii U to play the same game you can play on the old Wii?

What was Nintendo's plan here exactly? That sequels to Wii Sports and Wii Fit would keep them relevant to casual gamers forever? Nintendo lost the casual gaming audience and quite frankly, it shouldn't even be a surprise that they did. They haven't themselves made a huge completely *new* casual hit blockbuster game since Wii Fit in 2008. 

So 'core' gamers knew what Wii U was, while the rest did not. And the rest is the overwhelming majority.

Pricing is always a bit difficult. But it's not really like the average consumer thinks i don't get enough power for my money. It's more like people wanting to spend an amount of money. See 3DS/Vita. Basically the worse hardware sells way better for an almost equal price point and even for a higher price point.

Or see Wii/360. There was a time when you could get the 360 for little more or even a bit less. Still everyone wanted a Wii.

Basically the problem is, Nintendo never managed to make people want a Wii U.

You said yourself, how marketing is a small problem when you have some people didn't know that Wii U exist and some other people that thought that Wii U was an addon for Wii!?

Marketing, with high price compared to 360/PS3 and bad launch titles are biggest Wii U problems, that lead to terrible sales that lead to 3rd party abandoned them.

But the caveat here is even after we explained what it was, that it used all their Wii accesories and the multitude of other benefits of the Gamepad, blah blah blah (my store manager and I are big Nintendo fans so we def made most interested in it) it still wasn't enough because of its price compared to everything else out at the time. Had Mario Kart 8 launched with the system I am sure a lot more people would have walked out with  itregardless of the price because it was a game parents knew and liked from the Wii aside from Wii Sports. The 360 and PS3 were tough competition because of their libraries and prices during holiday 2012.