Even if Microsoft bought both companies (EA and SE) some how, PlayStation would still sell - just not as much, and Microsoft would be out a whole lot of money, sony would beef up their sports brand to compete with EAsports. Remember when you're buying a studio you're hoping to buy the talent too, i think everyone remembers what happened when MS bought out Rare prior to having a working relationship. All the talent left them, all that was left was an empty shell and some IPs. I do think they really messed up letting bioware get away from them.
I think it's been Microsoft's strategy to bribe companies for exclusive games instead of making the games themselves, which i don't believe is a great long term strategy, and often leaves games with timed exclusivity only - which probably makes fans bitter. If every company starts turning down MS paydays, MS would be in trouble - it's not exactly something they can control. Say if companies turned down all the offers, MS would have to offer more, and then if they get rejected they may have to offer even more, 3rd parties can get off pretty well this way. ME2 and Gears2 had to be very costly to Microsoft there's no doubt about it- in fact it's widely believed ME2 is a timed exclusive for this reason, and the fact its EA this time. Valve needs to get serious about ps3 development(if they haven't already) to get one of these lucrative deals, my guess is there was some kind of deal for l4d2, who knows if it's just timed like the rest of them.
