Harry Gregson-Williams would rock. The MGS2 theme remains one of my favorite themes ever. I definaltey would prefer an instrumental-only soundtrack.
And for the love of god, no Black Sabbath's "Iron Man". I pray I never have to hear that song again after the L.A. County Fair. I work for Hollywood Video, and I worked the booth there during the fair. We made the mistake of setting up Guitar Hero, and every single freakin' person that played that game played either Iron Man or Smoke on the Water. I had to hear those two songs nonstop all weekend. Besides, that song has nothing to do with the character, and putting it in the movie will only further the problem of people thinking it does.