IMO Castlevania III, Super Castlevania IV, Dracula X RoB, Bloodlines, SOTN, AoS, and PoR are the best Castlevania games. I liked III more than IV. Do yourself a favor and get a PC-Engine SCD emulator and Rondo Of Blood...it's so awesome!
DoS was also really good, but it felt a bit too much like AoS rehash like others have said. Still worth playing though.
Also regarding storyline, it's kind of like this:
Castlevania III -> Dracula X RoB -> SOTN -> AoS -> DoS
and
Bloodlines -> PoR