These are the current trends. The 'not allowed to love' one is more fluid than the 'not allowed to hate' one, with a large middle ground.
Not allowed to hate:
Castlevania III: Dracula's Curse (NES)
Super Castlevania IV (SNES)
Symphony of the Night (PS1)
Not allowed to love:
Castlevania Legends (GBC)
Castlevania Judgment (Wii)
Castlevania 64 (N64)
Castlevania: DraculaXX/Vampire's Kiss (SNES)
Castlevania: Order of Shadows (Mobile)
True Middle Ground (generally liked, but agreed upon that they're not perfect games):
Castlevania (NES)
Castlevania Adventure II: Belmonts' Revenge
Castlevania: Aria of Sorrow
Castlevania: Order of Ecclesia
The rest of the middle ground:
The Quirkies (these games have a following, but generally have one or more grating flaws that prevent them from being great):
Vampire Killer (MSX)
Decent game for its time, but Castlevania (NES) is pretty much better in every way.
Castlevania II: Simon's Quest (NES)
Decent game but improperly mapped out, difficult to understand without a guide, and some gameplay issues tack on as well.
DraculaX: Rondo of Blood (PC-Engine)
Pretty great game, but the control isn't as good as Super Castlevania IV. Still widely held in high regard, and for some, is a "Not allowed to hate" game. Also, the music is awesome.
The Mediocre (these aren't bad games, but they have a number of issues, enough to make fans generally recognize that they're not as great as we'd like them to be):
Castlevania Bloodlines
It's an alright title, but the rigidity of the characters, the missing color palette of the Genesis, and general lack of panache in comparison to Rondo and Super CVIV make this title fall into mediocrity by many.
Castlevania: Circle of the Moon
A pretty great title, but the (at the time) GBA display was just getting worked out, so the hero is tiny, the castle is huge, and double-tapping becomes a chore.
Castlevania: Lament of Innocence and Castlevania: Curse of Darknness (PS2 and XBOX for the latter)
It's not quirky... it's a cookie-cutter dungeon-crawler-style game with flat boring stages, even if they're visually appealing. The music rocks, though. Gameplay-wise, they're pretty OK.
Castlevania: Legacy of Darkness
People dislike it because they feel it is what Castlevania 64 should have been, thus they feel ripped off that it took two games to get it 'right'. There are some gameplay issues that, though at the time were acceptable, have made the game age in an unpleasant matter.
Castlevania: Dawn of Sorrow, Castlevania: Portrait of Ruin
These games are cookie-cutter titles that, while good, end up looking like copies of Symphony of the Night. Some issues in the art direction and a nonsensical plot, accompanied by some light trampling of prior Castlevania canon (from AoS and from Bloodlines) also make them gather some negativity.
The Unimportant (games which may or may not be bad, but generally people feel 'meh' about them. No true hatred, but no fire-in-your-belly passion either, save for a few):
Castlevania: The Adventure
Castlevania: Harmony of Dissonance
Castlevania: The Arcade
Castlevania: Pachislot
Current Hot Trends:
Castlevania: Lords of Shadow (has heated opinions both for the game and against it)
Castlevania: Harmony of Despair (has heated opinions from the item collectors and online community, but purists find it to be a cash-in)
THE ABYSS:
Really bad games we should hate (opinion) but no one listens to meeeee:
Castlevania 64 (Commodore 64)
Castlevania (Amiga)
If there's a game I've not mentioned, then it falls under "The Unimportant". That's how unimportant it is.
Let it be known that, aside from THE ABYSS, I think all the other games are actually pretty good. Yes, even that one. And that one. Yup, that one too.