And I think MS learned from that. Epic wanted to make gears cross platform and there is a leaked ps3 build out there. Then they wanted to stop the franchise so MS had to buy it. Mass effect was a big exclusive but EA bought bioware and then it went multiplatform. Saints row also became multiplatform.
If you look at Sony they too have learned from this. Now when they partner with a third party and the titles do well they end up buying the company if they are able too. Insomniac , house marque and so on and so forth.
IMHO MS should have bought Tomb Raider/Deus Ex+teams from Square Enix last year. A completely missed opportunity.