So far it's seemed to have been reviewed far more subjectively than most other recent games. It's been a while since a game's gotten this good of a score without massive marketing/hype influence behind it. At least stateside. I trust this site more now, seeing as how they're the first to give it a higher score than GTA IV, which so far hasn't lived up to the hype-inflated reviews according to most people who've played it.
There are of course hints that it may be ported eventually to the 360. Kojima was interviewed and asked this very question, although in a more subtle way. He was translated as saying,
Speaking about other platforms, this is a very difficult question, I must say. My biggest mission that I had to accomplish was to create and finish MGS 4 for the PS3, and that was my biggest mission so far. And I have to really sit down and think about what I want to do for other platforms after this when the game is released. But you know looking back, I think we used a lot of the power of the Cell processor, because I had to allocate correctly the simultaneous tasks that it offers, whether it's graphics, sound, program AI. And also the project got so vast it had to use the Bluray disc in a dual layer. And there were some parts that were really specific and only able to be accomplished on a PS3, in many aspects...so it's kind of difficult, right now... what I'm thinking is how I can change this around for other platforms.