If they had to cross-develop between PS5 and Xbox Two that might be a problem though.

Vita doesn't even have 3rd party support. Obviously the 3DS is better :p. I was talking about the PS4 for example.

Well I'm using vgchartz numbers and the U.K is a considerably larger gaming market than Germany.

No, I don't think Knack will outsell Mario in the long run. Did you read why I brought it up though?

I'm sure they are, I just thought it was pretty easy and obvious to pick out the 2 games that wouldn't have been bought if dengle bought a Vita instead of a 3DS

I haven't even bought a Wii U yet. Regardless, third-party support for the console will mean little to me. $60 is a tougher sell than $30-40. I expect to buy fewer than a half-dozen Wii U games at full price during its lifetime, most or all of them first-party. If I had to pay $100 more for the console, I would take longer to buy it and buy fewer games in the long run. Not good for me, not good for Nintendo, not good for the industry.

Well, that's ONLY true for the PS4. That never happened with PS1, 2 or 3, so the trend speaks against your point. And remember that PS3 was very hard to develop for. Do you honestly think Nintendo would have made as great games on the PS3 as they did on GC, Wii or Wii U? No, they probably wouldn't. And seriously, take a look at PS1, 2, 3 and 4. How much have changed? Really, how much have changed between each instalment? Not much. Now, look at N64, GC, Wii and Wii U. Talk about change! Say what you will, but Nintendo drives innovation in a way few other companies does. THAT'S what would be lost if they went 3rd party.

Because there is no need for it. I can buy the Nintendo games I want on the 3DS and the Wii U, there is no need for the current model to change.

The reason Nintendo games are usually the best of the best is because they are created with the hardware in mind. Using Nintendo's unique interfaces and game interaction is what makes them special.
I dont want to pretend to hold a wheel to play the next mario kart infront of the kinect
I dont want skype calls and achievements in my games
and i certainly dont want to have to use the Move instead of the Wii-mote.

I think the biggeest reason is nostalgia. For a lot of us, Nintendo means videogames and consoles.

Nintendo were the ones that made videogames a worldwide entertainment. How many japanese games were launched outside of Japan before the NES? And how many american games arrived here to Europe? The NES allowed that to happen. Also, while Nintendo wasn't the first to launch a console, they certainly are the ones that have been doing so for longer. SEGA is a shadow of what they were, SNK is gone and Atari is dead (or almost). We only have Nintendo from those times, and losing their consoles would mean the definitive end of an era.

Also, as some have already said, their philosophy when designing consoles and controllers is more open than the one the competitors have shown, and don't fear to try new things. Although after what happened with the wiimote it's clear that both Sony and MSoft have upped their game, one keeping Kinect and adding rumble triggers while the other one has chosed to add a touch pad to its controller.

Other hardware manufacturers may lack features necessary to Nintendo fullfil its vision, sometimes.

Zelda Ocarina wouldn't be achievable on a PSone for example. Not without some compromises.

Wii sports wouldn't be possible on ps3.

Brain trainning wouldn't be possible on psp.

And so on.

In 50 years from now, people won't know whether those are alternative PSone controllers from 1996 or not.

I hate how the industry is stuck in "winning formula" when it comes to input interfaces, and mainly Nintendo is innovating while others copy.