Thing is you couldn't even make a movie on the most popular game of the series, Metal Gear Solid 1, as it already has a lot of back history that the audience wouldn't be aware of and which you couldn't possibly cover adequately within a 2hr time frame whilst you also have to dedicate more time to the main narrative. As a game it's not a problem as you're not expected to playthough the whole story in a 2hr period so you have more time to flesh the narrative out a bit and offer information to the player which they can catch up to in their own time.
So yeh, I don't see MGS working as a movie unless you make some massive cutbacks to the story and shorten it up a bit, which wouldn't please the MGS fans, which in turn alienates your target demographic before you even release the movie, and frankly gamers have had enough of having game franchises butchered in their transistion to the silver screen, even if the adaptations are of fighting games which don't have the greatest narrative to begin with.