It's Microsoft's business strategy to put their "exclusives" on both Xbox 360 and Windows. They did that even for their crown jewels Halo and KOTOR, even when they did not have to. It's their CHOICE to put their exclusives on Windows. So, they're still Microsoft's exclusives because Microsoft secures that titles to make sure they don't go to Sony PS3.
On the other hand, if let say Microsoft loses a title because somehow Sony is managed to snatch it away from them, then you can say it's not an "exclusive."
For whatever reason, Microsoft seems to think of that as a good business strategy. I'm not about to fault Microsoft for a business strategy that they pursue because they think it's in their best interest to get their "exclusives" on both PC and Xbox 360.
It's the choice they make. It's within their control. Unlike, let say, Sony lost Devil May Cry 4 to Xbox 360, that's not the choice Sony made. That's out of Sony's control.
The main and most important point here is: If it's a Microsoft's "exclusive", that means Sony is not getting them -- because Microsoft makes sure PlayStation doesn't get them.
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