Uh..Metal Gear has been on a TON of platforms.
Konami is a third party developer, and Kojima's particular studio is good with spreading the love to other consoles. MGS4 may eventually make a move to 360, but with as high as production costs are these days, and as slow as the PS3 is at least initially selling, unless MG4 outperforms Gears of War, they aren't going to make enough money to make the game a massive success...At least not the success they got when they produced Metal Gear Solid 1, 2 & 3.
I see it doing extremely well, because the ps3 is a barren wasteland of good games, with a gem coming every once in awhile...essentially it's kinda like the good ol' Gamecube. Good games sell extremely well...everything else? Blah.
The main problem here is that the PS3, until it drops it's price, is going to be a very, very, very niche market. PS2 really well, cause it was affordable, so it always had a huge stable of gamers willing to buy products. PS3 won't have that, so it'll be interesting how it performs without it's usual huge player-base.
Leon's Sony-fanboy-ism is slowly being killed by logic and reason..someone hold a funeral.