I'd go with The Thing. It would be really cool to have a multiplayer, not knowing who to trust. It could have some pretty clever inversions of the movie, like forcing everyone to be tied down like Mac did in the movie, then just killing them when they're tied down. Plant fake evidence, hold hostages, run tests, locking people outside to freeze: It could be really good with some creativity. Yes, I know they made already made The Thing game, but it didn't have a multiplayer, and the second half was awful as you had to fight humans for the whole thing(No pun intended). So, what movies would make good games?