Honestly, I didn't even know there was a game or that this series was adapted from it. I saw Castlevania years ago because I found it on the internet as a recommendation and I watched it and really liked it. Mostly because of the monsters, the fights and the good animation. I paid very little attention to the story or the way the characters were developed, but for a dark fantasy and action anime it wasn't bad.
Nocturne is something that is obviously far from being as good as its predecessor, but it is decent in terms of animation and battles (although from what I saw spoiling the last season that I haven't seen yet, the descendant of Belmont was given a lot of "Power Up", but oh well, typical of the protagonists).
Otherwise I don't have much to complain about since it's an animated series for adults, that is, it's not for children and because of its explicit and gore content (a lot of gore, although not as much as in its predecessor series). But for me it's more than that: an action, dark fantasy and gore series to pass the time.
Good review.