Angry Birds

From a Japanese perspective:A mainline Metal Gear
From a Western perspective, I'd agree with the Bethesda exclusive.

If something a la Skyrim or Fallout were to become Nintendo exclusive, I would imagine that would cause a massive shift in terms of how a large percentage of gamers would view Nintendo favorably going forward. A timed-exclusive Grand Theft Auto in conjunction with that...

If both of those two things were to happen, Nintendo's reputation as the kiddie console would literally be fixed overnight.

Kingdom Hearts 3 would be big for several fans and gamers loyal to the Playstation brand expecting that have been awaiting it on a Sony console.

But the bigger impact/shitstorms would occur should Nintendo secure exclusive releases for the Madden or Call of Duty franchises. 

Eh, only if they stopped enabling purchases of previous versions on cellphones as well.

Final Fantasy for Japan. GTA for the West. Starcraft for South Korea.

Basically, it depends on where the shitstorm is meant to happen. Each region will get it for a different game.

CoD would be a big storm, but not that big. People would fully expect another non-exclusive within a year, anyway. It's the games that are released about once or twice a generation that would get the shitstorm reaction.

realistic?

ok even that is very unrealistic but maybe

dark souls 2

Realistic?

Kingdom Hearts 3

Da Hell?

A mainline Final Fantasy

WHAT IS THIS MADNESS!?!

Call of Duty

2 + 2 = Fish?

Halo

No. That makes too much sense.

I would be absolutely furious, the amount of wasted potential from putting a game like that on such an enimic console is just tragic, thinking about the possibilities of fallout next gen on powerful consoles and pc.

I know the PC modding community would be particularly angry.

How about if Nintendo rescued Darksiders and made it their own IP...I bet there will be a shit storm about that even though no really bought the games.

FFV13? That's peanuts compared to a HD remake of FF7.