Remedy and Mistwalker for mine, Harmonix would have been great.
Mistwalker (according to wikipedia) came into fruition with the help of Microsoft. Provided money etc, I think they are already and unofficial source of games, Remedy would be clever especially if MS doesnt want to lose Alan Wake and in fact push the franchise.
Harmonix for Dance Central and Rock Band. I think MS could have taken Rockband to the next level that it never seemed to take.
There are other companies as well, but the way I see it is MS seems pretty happy with 3rd parties ie Bungie and Epic. The reason Bungie wasnt bought is now pretty obvious I thought, I think MS didnt want another Rare case and simply buying a company doesnt mean anything if you dont have the people, MS couldnt make Goldeneye but Nintendo could for some reason. I think because of this MS is a lot more cautious.
