Arguing over whether or not Ghost is alive is pointless right now because no one will know for sure until MW3 comes out.
I personally like to think that he's alive. Yeah, the odds aren't too great considering he got shot in the chest then set on fire. But I'm sure he was wearing a bullet-proof vest of some kind that would have stopped the bullet and even if he wasn't we never technically see Ghost get set on fire, it was only Roach. So, he might be alive.
But like I said, that's only what I like to think. And we won't know for sure until MW3.