Castlevania has been adapted in other media besides game—gamebooks, novellas, comics/manga etc.—with varying amount of success. Personally, I think Castlevania has a lot of potential to also be succesful in other forms of media instead of only video games and nothing else.
What non-game Castlevania project would you like to see and why? Also, what would you like it to be about?
Personally, when considering a large part of Castlevania's appeal is the look of its world, a visual format such as an anime would seem like a natural choice to me. If it were to be a long running series, I would definitely choose to create an original story, but still keep it faithful to the aesthetics of the series. If it were say a series of about 12 - 24 episodes, I would do an adaptation of CV3's plot and the events surrounding it, elaborate on the characters, and overall give a detailed account of that period in the chronology. I would prefer this over adapting any other game since it would serve as a good introduction to the series, and I find other periods in the timeline to be hardly as interesting.