There's quite a number of routes they can take with their IPs and mobile. They can do a Wario Ware style game, endless running jumping mario game, a strictly jumping mario game, a kirby feeding game, an NES remix style game, some sort of puzzle game, a kind of NES zelda dungeon solving game, and so on. They could probably do all sorts of games if they wanted.

I wouldn't play them since mobile games aren't my things, but I recognize not every game has to be catered specifically to me, and whatever helps out Nintendo, I am mostly okay with.

They should really consider porting the old Pokemon games, similar to how Square has ported the old Final Fantasy games. Controls won't obviously be a problem with the combat being turn based and they'd be a good test of seeing how the IP would do on mobile.

Also, 2D Mario would probably be a good game to bring to mobile as well.

I Don't want Nintendo to do games like Endless Runners. I know that games like these, and puzzle games make the most money however, I'd like Nintendo to be Nintendo through and through on mobile. They try to innovate and be different so I hope they carry that with them in their endeavors in mobile gaming. I do think there should be some sort of Fire Emblem game as it's a perfect fit for mobile gaming.

Every single touch-centric game that made the DS huge should already be on mobile. That should just be the new platform for those types of games, because that's where the audience for them is now. Brain Age, Professor Layton, all that jazz. The people still gaming on dedicated handhelds are playing more "gamey" games that require physical controls, so those are the types of games that can stay on consoles.

The fact that Nintendo hasn't done this already shows how stubborn they are. They could have an install base of hundreds of millions, but they're only interested in selling a game on their own platform on their own terms.

Last thought, Animal Crossing would be PERFECT on mobile. It's exactly the kind of social game that's been huge for years now, and all of it could easily be done with just a touch screen. It could be free or even a couple bucks, and you can either unlock everything yourself, or the impatient types can pay to get tools faster, get furniture sets, make stuff grow faster, etc. It would be the perfect situation where the average person doesn't have to spend to have fun, but Nintendo can still make a lot of money from it.

I have seen a Pokemon knock-off game being played by my nieces on their tablets. Maybe there's potential there.