The only way I see this working is if they do a streamlined version of MGS3. Anything else associated with the franchise is going to fail. Why?
1) Lead actor. No matter how much you hope it will be the case, David Hayter is not going to be Snake. No production company in their right mind is going to bank a $100-200 million production on a guy who's last on-screen work was The Guyver 2: Dark Hero, and that was 20 years ago. He's got the voice, but he's in the same vein as David Bateman - there's a difference between a voice actor's persona and their physical presence. Bateman can pull off shady diplomats and politicians, but he can't pull off the physicality of a hitman who can go psychopath at a moment's notice (unlike his voice work in the games), and the guy who played him in the film failed at pretty much everything associated with the character. The last time I saw Hayter in a fanfilm/promo where he portrayed Naked Snake, he looked entirely at odds with the character, regardless of his voice.
2) Director. There's no way they're going to rope a big-name director into this, unless it's a studio project and they bring in an indie director who wants to cut his/her chops on a established property. Coupled with the stigma of video game movies and the property itself (see next point), I figure they'll have an insurmountable task on their hands.
3) Source material. I don't know how they intend to get across the story in a feature film. You can immediately write off MGS2, which was one of the biggest fourth-wall breaking games in history (to say nothing of it's insane plot). MGS1 and 2 had a cyborg ninja, a woman who dresses up like a male soldier, a guy who gets his hand chopped off and (supposedly) gets possessed via proxy by the spirit of the protagonist's dead brother, a scientist who pees himself in fright and more bizarre plot twists than you can shake a stick at. There's no way they'll take that material and put it in a feature film - it's intrinsic to the storyline and the series as a whole. Any adaptation is going to be neutered as a result.
4) Effects. The games rely heavily on mecha-walkers, with the later games having extended sequences featuring them. Unless they're prepared to blow their budget on making these things walk around without making it look like a video game, they'll have to keep them off-screen for long periods of time. That's something I don't think they'll have the luxury of doing.
Aside from the fanboys, I doubt there would be much interest in a film adaptation. Even Uncharted is stuck in development hell.