As much as I love Splatoon, way more than any 3D Mario, I can't deny that a brand new 3D Mario would probably get more people on board, it simply has way more history and is way more iconic than Splatoon, thus people are more likely to buy a whole console for it. That's what I think anyway. The best option would be to have both, though some people have brought a good point about having a consistent release schedule. I think Splatoon would hold it's own as the big holiday game.

Depends on the Mario game. A mario game like NSMBU that adds little to the franchise? Then Splatoon 2. A game like Mario Galaxy that is a leap above its predecessors? Then Mario.

At any rate, Splatoon just came out last year, so it'd be better for Spla2n to have a little more development time. Release it in year two with a legitimate single player component, and you're golden.

Super Mario Galaxy 3

The next Zelda being full NX exclusive would guarantee sales, but piss off the fanbase. A better choice, and most likely, will be a Zelda U port.

Also there must be a Mario 64 caliber game. The WiiU did not have anything like that, so fans will flock to it. A new Mario 3D world would be nice as well as that caters to a different style, but an actual adventure Mario is a must.

A proper metroid, current gen Donkey Kong, Earthbound, and a follow up for Star Fox announced for later in the pipeline. And last but CERTAINLY not least, a true console version of Pokemon with full online support (main game to be single player though).

If they do all of this, they could make a monumental comeback. If they do half of this at launch, they will at least be relevant to most of the console market again.

New 3D Mario simply because people are getting blue balls from not getting a 'true' 3D Mario this generation -- but that's only if the next 3D Mario carries the type of innovation and wonder that we expect from series. Splatoon 2 will probably simmer for another year or two and I wouldn't be surprised if Nintendo develops an anime for it in the mean time to keep interest high.

Depends...

If it's a creative 3D Mario with amazing visuals/ideas, I bet this would impact more. If it's 3D World-like, then definitely Splatoon 2.

Playstation is not responsible for whether or not Naughty Dog, or Capcom want to remake their games. Nintendo directly telling the fans that bought the Wii U that their money was wasted and bringing all their games to NX is a direct slap to the face to the people who were there when things for Nintendo were at their worst.

3D Mario. WE haven't had an original 3D Mario since Galaxy. If Nintendo could pull that kind of excitement again, NX would benefit greatly. Splatoon 2 wouldn't do bad either.

Capcom no, Naughty Dog yes. Also Heavy Rain and Beyond Two Souls.

I guess true enough (as far as Naughty Dog).