My gateway into the series was Super Castlevania IV. I actually owned a copy of Castlevania III before that, but I just couldn't get into the game the way I could with SCV4 -- but I think part of that was due to the absolutely crushing difficulty of the early CV games (Dracula X, the follow up to SCV4, returned the series to its crushing roots, and I cared less about that game because of it).
I think what appealed to me about the series was the simple nature of the story (good vs. evil) and the nods to gothic horror and classic movies. I'm a sucker for the Universal and Hammer films, and I appreciate a good homage to those series. But I'm not the best game player, so the really hard titles in the series didn't have the appeal for me of some of the 2nd generation titles.
Certainly Symphony was a fine game, but it marked a turning point in the series for me. Later entries, like Aria and Portrait, put less emphasis on the monsters you were fighting and brought the heroes to the fore-front... which is unfortunate because, like in the classic movies, the heroes aren't the interesting part of the series. I'd rather have a hero that's there to fight some evil (stylishly in his little leather skirt) then have to hear about him whine about _why_ he's there fighting evil (in his armor and his trenchcoat and with all his weapons...).
If I had to pick a game that came out after SotN that I did enjoy, that would be Circle of the Moon. I've gone back to that game several times. It's the right mix of old-school feel with SotN style gameplay.
Mao Edit: Just cleaning this double posted item out.
It double posted? How strange...
[insert unmerciful teasing here]
NOOOOOOOOOOOOOOOOOOOOOOOB! :U
I have shame my family. I have shamed myself. I am the worst kind of human being. I beg for forgiveness.
"And I will answer, 'No.'"