Guilty Gear - After seeing that short clip anime of it, I have always wanted an anime from it now. I think it would make a nice movie, though a season could be done since the GG series has some nice depth to the story.
Castlevania - Would make a nice horror anime. They could take the games and combine them to make one series or a few.
I'll think of more later, cause I know I had a few more in mind.