Listening to the music while playing again, I wouldn't say it's badly done, not by a long shot. Stylistically I wouldn't call it very Castlevania, but two things would make it great without totally compromising its uniqueness within the series-
1. Stage-specific themes. Basically, just more of it.
2. Focus more on being scary and less on being fantastic. (I guess I could say this about the game itself too.)
I guess what would really enthrall me is if the sequel had a lot more focus on its horror-driven roots. There were some twisted things like the headless burrowers and the scarecrows that made the 'Vania fan in me smile from ear to ear. Castlevania is an Action Horror game, after all.
Also, please no more QTEs. Of any kind. No more. These need to die already. Gameplay or cutscene - not both at the same time. If Gabe is doing something cool during a cutscene, I'd just like to enjoy watching without having to worry about pressing buttons. To me this is the thing that most brings God of War to mind; if there is something in battle that needs no more than a button press to execute, it should only last as long. I don't want a quick elaborate dismemberment cutscene; I want to smash the thing away and keep on fighting. The player should be in full control of the character, or none at all; if I have to press a button for an event to have it keep playing, wouldn't it be less work to just let the event... be a cutscene? Ninja Gaiden II did this kind of thing correctly, I think - flashy, but not so cumbersome as to interrupt the flow of battle, and WITHOUT A DIFFERENT BUTTON ICON ALL THE TIME. (Devil May Cry 4 is another example of some cool attacks without the use of QTEs.)