As far as I'm concerned X-box owners can have MGS4 and play it all they want. I got mine and I love it as I love my PS3. I see no problem in everybody getting to enjoy as many games as possible. I will however agree with Onmi that until the game actually shows up on the 360 people should stop bitching or buy a PS3. You don't hear me whining about not getting to play GeoW. If I want to do that I buy a 360 or wait (even if waiting is probably futile). So I don't play it and I don't whine. Cough up the green or shut up and wait.
Another thing though: I think exclusives is a good thing for me as a PS3 owner. At least that way I know that the game isn't a half assed port of a game made for 360. The developers can make what they want out of the hardware without needing to be concerned about fitting it on DVDs. I think that is part of what drives the technology forwards. (This argument of course works both ways). I am a bit pissed about having to play Fallout 3 on PS3 as it seems I got shafted. So, in some respects exclusives are a good thing. But in general I don't mind multiplatform. And at some point I'll get the money and buy a 360 (also, there need to be a bit more decent games for the damned thing) and see what the fuss about GeoW is about. Until then I'll shut up.
Also the image of the 20 DVD box of MGS4 is funny as hell, even if wildly untrue.

Have some sense of humor guys.
Now I have to go do something to silence the inner fanboy that really doesn't want MGS4 on the X-box because the damn X-bots can't have it all dammit.

He's an annoying jerk who pops up now and again. He and I have some serious arguments about what to think. Luckily I win most of the time.