Microsoft. They have by far the weakest first-party studios, which is why they constantly have to pay third party developers to make exclusives for them.

Because they haven't really done new ideas. Online was Sega's idea, and their controller designs aren't very original. Nintendo would have been my second choice, actually.

They would be gone though. They wouldn't be able to make games on Xbox or PS.

No really winner
Nintendo are too busy living in the 80's and 90's.
Sony have excellent hardware and 1st party developers but can be arrogant at times.
MS only really care about the bottom line.

Hard to say but i don't think we need Nintendo.
Sony and MS are pushing consoles experiences while Nintendo tries to play catch up.

You mean which one would be the least bad to lose, right? I refuse to answer until this is clarified.

The gamer side of me says Microsoft. They haven't been around as long as the other two, so their foot isn't in the door as much. (Although that is changing quite quickly.) As well has having the seemingly weakest first party offerings and the fact that they would still be around, just not muddling with gaming. However, that can also be said about Sony.

The last point, that is...

If I have to choose I say Microsoft, I have always liked more the Sony's first-party offering, even if I liked Halo too, just doesn't appeal in a whole to me. Nintendo is in 2nd spot for me, I wouldn't like they quit.

I voted Microsoft. They have virtually no first-party games (Halo? Gears of War? Crappy Kinect games?) They are also the newest, but it's pretty much following the same path Sony is with it's consoles, but Sony is doing it better.

If you say Nintendo so more could enjoy their games, that seems a little hypocritical to me.

OUYA. Because they're already irrelevant.

Close between M$ and -$ony neither are gaming companies primarily, and thirds dominate their identity. Gaming was fine before them, will be fine after.