I think it would just bury it.
Castlevania is a little more delicate than most others when it comes to attempting to seriously execute it, especially as another form of media.
We know it can be done, but in order to take it to the next level would require such skill far beyond Paul W S Anderson's. Whereas Resident Evil could work as a run n' gun zombie shooter, what can Castlevania honestly transition into?
Castlevania is pretty stuck in it's genre, a one man army taking on the legions of the undead lead by Dracula of all things. In order to properly pull this off with any seriousness you really have to work at it. Honestly the only other direction they could possibly take with this is just full parody mode and hand it off to Pixar for a kid friendly fun filled monster mashup adventure. Not saying that wouldn't also be interesting, but I would prefer some sort of seriousness to it.
Capture for me the visual and audio spirit of Super Castlevania IV on the big screen, and you will win me over.
Personally I think Simon's Quest holds perhaps the biggest movie potential, other than Dracula's Curse of course. Simon's Quest has a wide aptitude for expansion to include a larger cast, with many "NPCs" able to take up some roles. The ferry man, the towns people, the Crystal Knight perhaps given a bigger role. Hell you could make up new character that fit right into the setting. A crazy merchant is always welcome. Perhaps a Zead like character for Death's part. There is a LOT you can do with this. I can see comedy working it's way in easier like this than any other game. You have such a wide variety of expansion and established things to work with.
Open the damn thing with Simon and Dracula's final battle, and a possible short montage of the castle trek. That will get the audience's attention. Then tell of the aftermath, the curse, and go from there. Simon battles the undead bosses, Carmilla, Death, etc etc etc while traveling the countryside on a varying set of backdrops. Finish it off at the castle ruins with Dracula wraith, and burning the count 'forever'. Looks great in my head.
Honestly this doesn't sound as hard as I thought. Too bad it'll never happen though.