My first Castlevania game was Castlevania 2, which creeped me out a lot. Especially later on. Remember how as you got closer to Dracula's castle the towns got less friendly until the last one was completely empty except for that insane guy? On the other hand, it was too easy. I got C3 expecting the gameplay to be similarly easy, but got a surprise. A good surprise; challenge is something I really enjoy in games. C4 was less challenging but very well designed, so I give that one points as well.
For that reason, I had mixed feelings about Castlevania: Symphony. There was a lot of good stuff about that game: the graphics, sounds, and music are all great, and the monster design is creative. Howeve, about 1/4 of the way into the game the difficulty pretty much disappeared, in my opinion.
Since then I haven't played many Castlevania games. I managed to find C1 a year ago and that was fun, but other than that...nothing, really.