I dunno who they could get to play Snake, though Hayter doesn't look like Snake, so that would be a no-go.
Casting Snake would be an iffy call, one that I wouldn't want to make, and we don't currently know their budget. My bet would be on either a talented New Comer or an Unknown... Unless someone big name like Christian Bale or Hugh Jackman was after the role. It also depends on whether or not they're going with Older or Younger snake, I always thought of Solid Snake as being perpetually near 40ish, so I think an older actor would be a better choice.
My problem with Hayter being cast as snake is that he doesn't look 'hard' enough, too baby faced, that and he hasn't 'acted' in ages and while he is a GREAT voice actor I don't know if he could pull it off. Kojima wants him cast as Snake though, so it might happen anyway.
One actor who might have the right look (IMO) is Thomas Jane but I'm unsure if he has the actual acting chops.
I've put up a new thread so we can stop derailing this one with MGS Movie and Casting discussion.
EDIT:
Bioshock will be the best Game/Movie adaptation...period.
It is being directed by Gore Verbinski, who is quite talented despite some bad scripts, but the script is being written by John Logan. Who is responsible for the upcoming Lincoln Biopic from Spielberg, The Aviator, The Last Samurai, Gladiator and Sweeny Todd.
So barring a fuck up of incalculable proportions... this will probably be the best game-movie adaptation anyone could hope for.