First thing I would consider is the game/series itself in comparison to game length. Take Metal Gear Solid for example, which I think would be absolutely perfect for movies for obvious reasons. Considering the games are cutscene heavy, you can still realistically beat them in a few hours. So already they are close to "movie length". It would be entirely possible to cut certain parts of the game out and still cover everything needed to satisfy fans and make a good movie. If the games were several hours long, 30+, you could plan for multiple movies instead of trying to fit everything into 1 movie and possibly removing important parts.
One thing I have to disagree with that I read in the comments is that they should do some thing unique and NOT follow the plot of the games. As a fan of the games I would love to see movie versions of the games played out that properly follows the plot. Seeing what they did for Mandarin in Iron Man 3 was absolutely terrible imo, and one thing I always hated about the X-Men and Wolverine movies is that he's never worn the iconic Wolverine costume.
Using Metal Gear Solid again as an example, if they changed that story in any way to differentiate it and called it "Metal Gear Solid the Movie" I would be extremely disappointed.
So what would it take?
Since I mentioned it enough, I think Metal Gear Solid would be the best candidate for a successful video game movie franchise. Start with Metal Gear Solid, and that opens up all kinds of potential for the sequels or prequels much like the videogames.