It's a simple question. The question is from a buisness perspective for nintendo, so think about what the price of the company should be, compared to what nintendo might gain from it. 

Personally: Mistwalker, Platinum Games and Slightly Mad studios. It would be cool if they managed to get sega or square enix too :p

Well, I think you've already mentioned all the good ones :P

Platinum could be good, or Mistwalker, and Sega and/or Square could use the Nintendo touch ^^ Besides, they both have certain mature franchises Nintendo could benefit from.

But, what they really should do is buy more Western studios...

I mentioned slightly mad, they are making the new cars game that is coming out. Nintendo has a certain need for (a) speed car sim. I would like one like burnout.

It would be pretty cool if they bought bethesda though, not that it's going to happen though ^^  

Platinum games and Nintendo complete each other.

And rename them to infinity money. Seems legit.

EA. that would rock the industry

All nintendo games would require origin. Imagine that. Nitendo games needing internett to play.

To be fair, platinum wanted MGR on wii u, but konami didn't.

Platinum games
Mistwalker
Obsidian
Sega
.... Enough new IPs and innovation for one generation.

Sega and Platinum could do Action/FPS/Adventure

Obsidian and Mistwalker Would obviously do JRPG/WRPG

Could've bought Bungie to fill their online FPS gap.