Well since you have played Metal gear Solid you know that the length of the game is only as such because of the tasks and trial and errors of the game player. If you were to only go about by the game's cutscenes and major conflicts then the three games that I've played would probably run out to be only a couple of hours though I believe that MGS1 would be a bit shorter as it's the shortest in the series.

If they can make a parallel or perhaps even better representation of the characters from the game's cutscenes, then they would be able to make a quality film. I believe a special edition of MGS3 had a DVD of the game in nothing but it's cutscenes and it turned out to be in the amount of length that I mentioned above. All in all it just takes a group with a passion.