I think the story has the potential to make a good live action movie. Unfortunately, the BEST we can realistically hope for is a piss poor imitation of Van Helsing, and we probably won't even get something that good.
The studios have never done a video game movie justice, no matter how good the game in question is. The problem is that as a source of material, video games aren't considered "serious" enough to warrant any kind of respect. So they'll deviate widely from it to try to attract a larger audience. Elements that made the game successful will be discarded in favor of elements from other (more successful) movies. It has to do with sales figures. Even the best selling video game on any given year doesn't make enough money for the studios to think of it as successful on its own merits. For them to sink the money into developing it as a motion picture, it will need to have wider appeal so as to garuntee more tickets will be sold.
Just look at what they did to DOOM. Scary atmosphere, great premise, lots of action. It should have been impossible to fuck up, but they turned it into an action vehicle for Dwayne "The Rock" Johnson. They took out the idea of monsters from Hell (wouldn't want any controversy, now would we?") and replaced it with some lame "evil virus," gutted the gore and violence, and included only a few references to game "specific things," like the BFG-9000. In short, the end product had less in common with DOOM than Ghosts of Mars did.
I'm sorry to say this, but we're probably about to see something that will be Castlevania in name only.