This is just a fanboy post but I love castlevania.
Not just for it's gameplay but for it's story.
I don't know...well...any games that keeps a long of a story line as castlevania and to keep it on track. (like some games do)
I found a site that tells the COMPLETE storyline of CV and it's impressive.
They even have a family tree of the CV characters.
Some of the CV are alittle bland...(Dracula X for SNES) but it's the story around it that made me want to beat it.
That's what I like most about CV is that it has an intertwined story.

If you have a few to spare then I recommend you sit down and read what this site has to say.

http://www.vgmuseum.com/mrp/castle.html