It's been a long time since I played Castlevania II: Simon's Quest, and I think it shows.
I played the first Castlevania a lot, and the second one... I never really played all that much. It was very different, but that wasn't the problem. I liked the adventure-style 2-d games like this and Zelda II (yes, I liked Zelda II).
The reason was that I played this game without a manual, which was hard enough (especially without Internet access), but I also had an aversion to making maps of games as I played them, so I usually had no idea where I was in the game relative to anything else. Stumbling around blindly in a game like this one is a recipe for failure, and that's what I did. A lot. I did manage to stumble into a few of the mansions and clear them out. This was after I found a password in some magazine or cheat book or whatever and I could just wander around with a super-powered Simon.
I would eventually manage to finish the game... after watching a VHS tape of someone else putting in a password to get all the goodies (which I copied) and then just waltzing to the end of the game and stunlocking Dracula until the ending played (which I also copied). That got me the worst ending (as it should), although I didn't know that there even were multiple endings until much later.
I tried to play it again recently, and I'm still bad at it. The unlimited continues helps a little bit. I should also probably try to make a map if I want to take a serious stab at it. But that sounds like a lot of work and this backlog isn't getting any shorter...