Alright so let's rank them all.
S tier:
Aria of Sorrow
A tier:
Order of Ecclesia
Symphony of the Night
B tier:
Dawn of Sorrow
Portrait of Ruin
C tier:
Circle of the Moon
D tier:
Harmony of Dissonance
Aria of Sorrow gets to be at the top because it executes everything flawlessly: level design, variety of weapons (based soul system), good soundtrack, intriguing good story, and awesome art style. The re-playability is solid with hard and Julius mode. Finally the pacing is good and is not a broken as Symphony. That and the fact that the game is very cryptic (bat combos, magic spells, getting to the inverted castle without a guide) place it underneath. Ecclesia is probably on par with SotN. While it has many of the features that make Aria great, the Castle itself is a little lackluster. I know the game takes place in many locations in order to make it less monotone to play. But it was a bit detrimental to the castle design which wasn't a good call IMO.
Dawn and Portrait follow the formula to the book. In the process they do seem to be a little bit less memorable. Also, the anime art-style was a terrible choice that immediately made me not dig those 2 games that much. Portrait in particular has a very annoying cast of characters.
Circle of the Moon was an outstanding Castlevania given the limitations of the era, but it has been superseded in every way by the handheld sequels. The card system was a good idea but poorly executed due to the drops being very rare. Also, the game is surprisingly hard.
Finally, Harmony of Dissonance. It baffles me that this game was developed at the same time of the one at the top. Its only redeeming quality is that it had the most innovative use of the secondary weapons with the spell books. Apart from that it looks ugly, the soundtrack is awful, the level design is all over the place, and it's broken from pretty much the beginning as Juste is way to OP.
Despite how sad it makes me that we may never get another Castlevania by Igarashi. He and his team put an outstanding amount of quality games in a short timeframe. I'm ahppy I least I got the chance to play them all.
