"gaming companies" includes Developers, Publishers and the Big 3. Got the idea from the recent rumours about Valve and SONY teaming up to make PS4 (Which has been shot down by the way). You can have as many companies in the partnership as you want.

E.g: Game freak and Bethesda for an awesome 3D open world Pokemon RPG.

Nintendo and Rare making a new Banjo-Kazooie game? :(        (Nintendo alone should be able to make a great game with the IP, even without the old Rareware guys)

Well lets be somewhat realistic.

My biggest combo would be Eidos Montreal and Crytek. The first military shooter that employs the depth of Deus Ex a true military simulator where every decision shapes the out come of the game.

Sonic Team and Nintendo EAD Tokyo. Creating the first cross world game featuring both Mario and Sonic who get trapped and teleported to each others worlds. They need to find answers and get back home but how. Mixing the two biggest franchises and the two finest plat forming companies together.

Myst walker and Game Freak, over seen by Pokemon company Mystwalker and Game Freak combine forces to make the most in depth Pokemon console game ever made.

Square Enid and Nintendo. They had a joint studio and while I know Genius Sonority still works with Square and Nintendo still has some influence. After Crystal Chronicles it became apparent that Nintendo and Squares expertise combined is simply amazing.

BioWare and Nintendo EAD Kyoto (Zelda team). Bringing a Zelda MMO to the world the creators of some of the best western RPGs in the world are best suited to bring Zelda to the world.

I can think of another dozen studio combos from mobile phone developers to DLC Nes to full blown content.

Bioware and Yakuza Team coming together to make a third person shooter would be great. Yakuza Team could teach Bioware how to make something good.

Shlump

Capcom + Activision + Square Enix

We will call it The Whole Cow.

Sony, MS, and ninty release a console....id love to see what happens :P

Probably wont turn out too good though...

xD It would probably be great at first. But there would be no competition on the hardware side of things for a while.

parternships never work out as expected. I mean look at activision-blizzard. Blizzard likes making sequels once every 10 years, and heavily supporting them in between, while activision is just dieing to think of a way to release 2 cods yearly without recieving too much backlash. Sometimes each companies' strengths don't rub off on each other even if they are in partnership.

RPGs - Bethesda & Bioware
FPS - Bungie & IW/Treyarch
TPS - Epic & dunno ???
Action Adventure - Naughty Dog & Santa Monica
Adventure - Nintendo & Rare
Platformer - Nintendo & Rare
Sport - EA Sports & Konami
Survival Horror - Konami & Visceral Games
Hack n' Slash - Santa Monica % Platinum Games
Multiplayer - Zipper & Insomniac or Bungie & IW/Treyarch
Puzzle games -Level 5 & Atlus