For me it feels overrated and kind of obsolete compared to the Nintendo DS entries.
Dawn of SorrowJust an evolved form of SotN & AoS, new screen touch gimmick, better level design overall.
Nice music overall.
Portrait of RuinA new iteration on the level design format: independent different worlds linked to
by the main castle and with many small visual and/or interactive details (take the Victorian level interior as example), very cool.

New two character setup: you play with two different characters "at the same time" with some different skills each. Cool but gimmicky.
Nice music overall.
Order of EcclesiaA new iteration on the level design format trying to be a mix of "ancient" and "new" Castlevanias.
Only one character again but with new ability gimmick.
Some good music tracks among many mediocre ones, and weird backtracking choice on audio quality.

For me at least DoS and PoR are already better than SotN in gameplay and level design.
Still, SotN is superior in terms of audio quality (obviously) and musical composition to the point I can some times actually enjoy the OST out of context.
If you want some light insight into the development of SotN, see an interview here:
http://shmuplations.com/symphony/Unrelated: then later came Lords of Shadow (the first one, 2010), which was kind of an "old style" linear Castlevania mixed in
with 3D and other gameplay gimmicks (like the magic system) and a good, mostly ambient style OST.
Best 3D game in the series for me. I don't understand why some people hate it.