Another problem with making a movie based off a game is that games these days are very long. You can't very well cover a whole cv in two hours when the games take several hours to complete. You also can't spread it out over a couple of movies because the high point would be the fight with Dracula and people aren't going to want to watch a movie in which the hero is going to fight Dracula and doesn't get to it until the sequel. For example, let's look at SCV4. The first movie would be Simon journeying to the castle itself going through the drawbridge, the stables, the forest with graves, the marsh, the river, the caves, the waterfall, the submerged city, the skeleton fortress, the rotating dungeon, the endless tower, etc. until you arrived at the actual castle. Actually, that might take more than one movie. Plus, unless you added characters, these movies would be nothing but the hero killing monsters.
The only CV games that could realistically be made into movies are the ones with a lot of cutscenes. Of course somethings like characters and interactions would have to be added and some existing story material would have to be omitted.
That being said, the only way in which we would get a decent CV movie is if instead of basing it off one particular game, it was an original story based off of the elements and existing overall storyline of the series. For example, lets take two gaps in the story: immediately after SotN and the 1999 battle. These are the only to things that have not been touched on in the games. We know these events happened, but we don't know how they happened. If someone who really knows the overall storyline is creative enough, we could have two really good movies that wouldn't butcher any games because they aren't based off of existing games. Also, if this was done, we wouldn't necessarily need those games to be made. We would just have the movies instead. They could also give closer the existing timeline.