I could easily see Killzone being a movie and a good one at that. They have never been able to make a really GREAT videogame movie. It's the fact that games are an experience, rather than just a narrative and no one has been able to translate that to a great story just yet. Right now Halo and Metal Gear Solid are in the works, but I'm not looking forward to either of those.
Halo's art design is just lame and a little TOO sci-fi for a war movie (Doom, Starship Troopers anyone), it usually comes off as being cheesy and low budget looking. Not to mention Master Chief is a faceless character, Denzel Washington wants to play him, but WHO is Master Chief really?
MGS suffers from the games being designed like movies in the first place. Hideo Kojima keeps pumping out masterpiece after masterpiece and it would take a hell of an effort to get it right. Not to mention Snake's story has been told in it's entirety. So unless Kojima wrote and/or directed it (right now he's not up to do either), I don't think they'd do it justice.
But Killzone on the other hand would make for a great movie, it's got a good story for a war epic and great art design (which is grounded in reality and not TOO far fetched). As well as a group of characters we've come to know, but haven't been developed yet. I can see it in the mold of Alien or the new Terminator. What do you say Movement?