Just because I know there are gonna be a good number of people saying this one, I won't mention Symphony of the Night (though that is my true favorite), and instead go to my next favorite, Order of Ecclesia. I feel that it is the only entry in the series since SotN that has actually managed to be as good as that masterpiece was. Through incredibly memorable music, intricate level design, punishingly difficult bosses, and beautiful but strong female protagonist, OoE manages to stand out as a triumph amongst the other two still-good DS Castlevania games. That's my opinion, at least.

Probably SOTN because it was just so damn good... Aria of Sorrow and the Dracula X Chronicles remake were pretty great as well. Can't forget about Lords of Shadow either. One of my favorite games last year.

Aria of Sorrow, Castlevania 4 and Castlevania 64 ( yeah, I'm serious. It's awesome.)

Probably SOTN as well, though I also loved Aria/Dawn of Sorrow. They're really well made, diverse, well paced, and the RPG elements stroke right into the completionist part of my brain. Never could get into more traditional Castlevania games besides that Dracula X remake for the PSP.

Super Castlevania 4. The most genuinely challenging of the series. 

Castlevania: Melancholy of Moonlight
Castlevania: Anguish of Memories
Castlevania: Chambermaid of Concupiscence.

Those were my three favorites. Though MoM does hold a special place in my heart. Though CoC wasn't too bad.

SotN because upside down castle.

I'll jump on the bandwagon and go with Symphony of the Night as well. I think it just hit the right combination of gameplay, story, and presentation. Especially at a time when there wasn't really a metroid game so it fit that niche so perfectly. Second favorite will be the black sheep of the series Castlevania 64, I actually really enjoyed it and had some interesting plot. I'm not saying it's good, I'm saying I liked it. ha ha

1. Reverie of Despondence
2. Torment of Fortitude
3. Eclipse of Decadence

Portrait of Ruin

Symphony of the Night.

@FourWude: Hm, my faves are:
 

1. Reverie of Despondence
2. Torment of Fortitude
3. Eclipse of Decadence

RoD was damn good but I will have to disagree with the others. If you're willing to stoop as low as having ToF in your list then you might as well have the following:

Sanctuary of Disdain
Iniquity of Mirth
Vexation of Contemplation

And how could I ever forget the most underrated of all Castlevanias, Lugubriousness of Inception. 

Symphony of the Night, since that game pulled off Metroidvania so well that people still call it Metroidvania.

Kid Dracula... 'cuz its adorable.

Easily Super Castlevania IV. Great music(the best remixes of the main themes from the previous 3), graphics that still stand up today, great gameplay, long game not padded with backtracking, and just the best overall traditional 'vania game out there.
 
I have to throw a shout out to the new 'vania game, Lords of Shadow. At first I was playing it with biased eyes, as I mistook it for a GoW clone, but the more I played it, unlocking new moves and just having a better understanding of the combat engine, it really grew on me. Turned into one of the better games I've played this generation. Sure, it stole from a few others, but these days, who doesn't? The overall experience was grander than it's few flaws. Plus, they did a remake of the Waterfall level song in IV for the new game, the only remixed song. Great story. SPOILERS---- I loved the original origin of the Vampire Killer in Lament of Innocence, but this one was a great origin story for ol' Drac.----

Castlevania II: Simons Quest. Personally my favorite. Not trolololing.

Symphony of the Night for its openness, character progression, spritework and soundtrack. My second favorite would have to be Order of Ecclesia. It lacks Symphony's openness, but it's aesthetically fantastic, the glyph system is great and the game's a good challenge (especially on Hard mode with the level cap set to 1).

Rondo of Blood is easily my favourite of the old-school ones. The level design is amazing, with tons of secret paths leading to hidden powerups, optional bosses, alternate stages and other stuff. Fuck, there are even secret paths that have secret paths in them. Oh, and the boss fights are some of the series' best.

Symphony of the Night.

Super Castlevania IV (still some of the best music the series has), SoTN (wonderful melding of adventure/action/RPG), Castlevania III (great challenge).

It's probably a three-way tie between Symphony of the Night, Aria of Sorrow and Dawn of Sorrow. SotN was pretty easy and seemed like it went by fast, but I love the weapon choices in it. AoS was my first Castlevania game and I fell in love with it. DoS is the best DS one IMO, its pretty much a bigger AoS. Both the Soma games have my favorite game mechanic with the soul collecting. I'm replaying them all right now and I hope the Sorrow games hold up as well as I remember!

The original is special to me as it is the first videogame I ever played. There was a nintendo at a friends house and it blew me away I literally spent hours playing and never got past the mermen in the first level.

Lament and Judgment (w classic controller) because they have the best combat and best game feel / gameplay engine. Lament also because it has the best atmosphere in the series.

No contest Lords Of Shadow.

A tie here for Castlevania IV and SotN. IV is just a masterwork of gameplay balance, atmosphere, and music. SotN's praises are well known, but the music, Alucard's character design, and sense of exploration stick with me most.

Lords of Shadow, Symphony of the Night, and Portrait of Ruin have to be my favorites. Lords of Shadow has to win though. I remember being so bored by the quick look and demo but decided to give the game a chance. I was drawn into the world and characters and it became one of my favorite games of all time, can see why people would disagree with me though. Portrait of Ruin and Symphony just had some amazing music and were a lot of fun.

1 super castlevania 4 - snes

2 castlevania rebirth - wii

3 castlevania rondo of blood ( dracula X in japan - pc engine

Every one of them starting from SotN up to Order of Ecclesia. Harmony of Dissonance is pretty weak though.

SOTN because it's the right answer.

I really wish I could make it an either/or based on the old style or new style, but I won't cop out like that.

Castlevania 3. It takes the original linear Castlevania structure and gives it branching paths and multiple playable characters you have to unlock. It also introduced Sypha.

Probably Dawn of Sorrow because of the Pokemon, but all three DS Castlevania games are amazing.

I really, really like Castlevania 3. The different characters are all interesting, the stages are plentiful and varied with a lot of really different challenges in them, the way the path forks at times gives it some nice replayability, the music is fucking fantastic. The only way it could have been better is if there was a separate button for sub-weapons and if some of the bosses didn't end up being reused several times. Also Grant's wall climbing ability is kind of hard to control, it'd be good if there was a separate button for that as well.

Now I didn't play more than a few hours of SoTN until I got Dracula X Chronicles for PsP, it was pretty great and fun, I even got the Crissaegrim on the first run without even knowing about it, boy was that a surprise. Aside from what I played of Rondo of Blood to unlock Symphony though, I didn't really touch that game for a long time. It was,y'know, hard.

Eventually I decided that I wanted to finish it and suddenly everything clicked, I started prefering to use Richter over Maria, I started finding all the secret paths, bosses and enemies became less of a pain because I became more patient. In the end I recognized it as one of the best Castlevanias, it will however never beat out 3 from the number 1 spot in my heart.

I also really liked all of the DS Castlevanias, actually I should get to replaying Ecclesia one of these days.

Rondo of Blood, easily. Just a fantastic side scroller, and tough too. Super Castlevania IV is also very much worth a mention, as is y'know, Castlevania. SotN is pretty awesome too, but I still prefer the older style Castlevania games personally.

Super Castlevania IV is my favorite with Dracula's Curse a close 2nd. I'm not a fan of the Metroidvania style so Lords of Shadow is the first game in the series that I've really liked in a long time.

Well mine would have to be Symphony of the Night of course. I just can't stop going back to it. I loved everything....EVERYTHING about it. The music just takes me back heh. I got to play that first on the Dracula X Chronicles with Rondo of Blood which I can also say is in my top list. Along with Castlevania: Bloodlines and Super Castlevania IV.

I also want to mention Circle of the Moon because I really liked the magic system even though it isn't as extensive as Aria of Sorrow, I just like the mixing and matching to get different effects and it was a pretty good game overall. Then there's Castlevania 64... the mood of it was different from the normal Castlevania but I still liked it. Maybe it's my love for the N64 or just Castlevania in general. I don't know

On a side note, I'd like to point out that this game DOES have music. I love AVGN but if I hear another person quote him about how CV64 doesn't have music ... I'm just going to go crazy LOL!! I will admit, the game has a good chunk without music but that's usually when you are outside, in the Forest of SILENCE. Sorry about that.

Castlevania IV for the SNES - the music still sticks with me to this day and is my favorite in the series, and the graphics were amazing to me back then.

SotN is a very close 2nd.

SotN. It was 1997 and I was 14. You never forget your first.

SOTN.

I really enjoyed all the DS ones but probably Dawn of Sorrow the most just because soma.

Lords of Shadow was also amazing. Loved every second of it.

@RockmanBionics: I got that for the PSP also, just to have another copy of SOTN. What a bunch of dicks putting it behind Rondo, so god damn hard.

Castlevania lament of innocence

Castlevania dawn of sorrow

super Castlevania IV

Castlevania, Castlevania III, Castlevania SOTN

super castlevania 4. because diagonal whippiness.