Melee outsold Double Dash.

According to VGChartz tracking by 120k, witch means a virtual tie. However Mario Kart gained a lot of populairity on the Wii, where it outsold Smash 3:1(though MK Wii was more heavily bundled).

"more heavily bundled"? I don't recall any kind of even-remotely-official Brawl bundle. And you speak as though the Wii versions were the most recent versions, when they're obviously not. Mario Kart Wii sold nearly 35 million copies... yet Mario Kart 7 is only at 10 million (plus digital) - Mario Kart Wii sold over 13 million in 2008 alone. And Mario Kart 8 is only at 2.75 million (plus digital)... unless you believe that Smash isn't even going to make 1 million (and if you do, then you're delusional), you don't expect MK8 to outsell Smash U 3:1.

All signs point to Wii U being more like Gamecube than Wii in terms of sales patterns (as in, who is buying it, proportions between types of games, etc). So we should be looking at Gamecube to get a sense of sales.

Furthermore, you are ignoring the question of who is buying each game. Mario Kart has always had strong synergy with classic Mario games (that is, NSMB Wii and Mario Kart Wii, Super Mario Sunshine and Mario Kart Double Dash, etc). Many of those who bought Mario Kart 8 would have already had a system for Super Mario 3D World or NSMB U. On the other hand, many Smash fans are big on fighting games and the insanely fast-paced multiplayer of Smash itself moreso than Mario or anything like that. Thus, it makes sense to expect it to sell to a lot of people who wouldn't otherwise have bought a Wii U.

I doubt there will be that much of a "long term" for the Wii U. Internally I think Nintendo has already started to shift resources to the 3DS successor that is going to need to come out in 2016. Gotta start working on games now if you want them ready by then. 

I think the Wii U will get whatever Nintendo already has promised (the 2015 games) + maybe like Metroid and Diddy Kong Racing game and some smaller projects before they put it out to pasture. 

I think the 3DS is never going to live up to their expectations in the West. Too many kids are iOS/Android crazy here and that's getting worse by the year not better. 

Next year is going to be interesting, Gamecube had a pretty strong software lineup in it's first two years, I'm curious how the Wii U's 2015 will hold up.

@Poll. Possible but I'm skeptical.

Wii U has shipped ~1.3 Million in Q1-Q3.  Double will be 2.6 Million in holidays, but doubtful it will make that much.

Nintendo's estimate which they did not revise is ~2.5 Million in 2014-Q4 and 2015-Q1 combined.

Apple is going to sell 170 million iPhones alone this year. Nintendo probably will struggle to sell 11 million 3DS'. 

That doesn't obviously iPad/iPod Touch or Android devices either, but every time I got to an airport, and I travel a lot for work, the amount of kids playing on their parents iPad/iPhone outnumbers the amount of 3DS' I see by 10:1 easily if not more. 

There isn't going to be a counter-trend here, the smartphone is a real part of people's lives and the first computer interface most kids are getting these days. I see 3 year olds that can operate an iPad. Like radio, TV, it's just a game changer for society. Saying the smartphone is a "trend" is like saying the internet is a trend (and some actually did argue that in the mid-90s). 

If I was a parent who really didn't give two craps about video games (even if I did), I think I'd be quite thrilled that the kids are occupied playing some free/$1 game rather than having to buy all of them $40 game cartridges. I don't think parents are protesting here and the kids aren't either. 

In any case thought the 3DS turns 5 years old on Feb 2016. It needs to be replaced, it's definitely no DS. 

What I'm starting to realize is that "better" isn't actually always "better". 

It's kind of like walking into a McDonalds or Burger King and trying to tell the people that a three course meal with a nice bottle of wine is better than the food they're about to eat. 

Well, yeah ... ok, but given the choice some people just a $5 burger + fries + and a Coke. Some times you don't want to go to a fancy restaurant and wait 30 minutes for your food to come out and spend $60+ on dinner for two. 

That's kind of the issue I think portable dedicated gaming is running into. On the go, people just want to something simple that hits the spot and does it for cheap ... if they're going to spend $30+ on a game, they're going to do it on one of the "big" consoles. 

At least in the West, this is the dynamic that is beginning to cement itself, the 3DS is kind of in a weird spot, where the games being more complex and more like home console games isn't actually a bonus. 

In either case though like I said, Nintendo is likely already full steam ahead in software development for the 3DS successor. I suspect Mario Galaxy 3 (or whatever the next Mario is) and Animal Crossing next are development for it already. Nintendo is going to want a gaurunteed strong launch this time after the problems with the Wii U/3DS, that's at least one problem that they have control over.