I think that with each passing day I get more and more impressed with the quality of Castlevania (and also the awfulness of some games that should not be mentioned ̶ S̶i̶m̶o̶n̶'̶s̶ ̶Q̶u̶e̶s̶t̶).

So far, I’ve beaten 9 games in the series, which are:

Castlevania: Order of Ecclesia (included in the collection, already beaten before on the DS. It’s actually my favorite Castle)

Castlevania: Dawn of Sorrow (included in the collection)

Castlevania: Portrait of Ruin (included in the collection)

Castlevania

Castlevania: Symphony of the Night (couldn’t miss this one, right?)

Castlevania: Harmony of Dissonance

Castlevania: Aria of Sorrow

Castlevania: Circle of the Moon

Castlevania: Dracula X

This collection brought what I consider the best Castlevania ever, which is Order of Ecclesia.
A truly passionate game (̶ Sh̶a̶n̶o̶a̶ ̶t̶o̶o̶,̶ ̶h̶e̶h̶e̶).
The artwork in this game is simply magnificent. Dracula is, in my opinion, the scariest in the series when it comes to design.
The gameplay is simply amazing, the glyph system is very well-explored, and you don’t depend on luck for their drops since they’re relatively common. Even the rare ones are not necessary to progress (̶ r̶i̶g̶h̶t̶?̶ ̶D̶e̶c̶a̶d̶e̶n̶c̶e̶ ̶o̶f̶ ̶S̶o̶r̶r̶o̶w̶).
The animations are fantastic. A good example is Shanoa’s double jump, which I consider the best animated in the whole series.
The best OSTs in the entire franchise, I’m sure of that! Some examples are Sorrow’s Distortion and An Empty Tome.

One of the few negative points for me is the repetition of certain areas, like the underwater section of Kalidus Channel being almost identical to Somnus Reef, and Tristis Pass being basically a recolor of Tymeo Mountains.
Even with that flaw, I’d easily give this game a 10/10, it’s simply outstanding. The bonus mode with Albus is pretty fun

Moving on to Portrait of Ruin...
I was surprised! I never really gave this game a chance, but I can safely say it’s the third best Castlevania I’ve played (only behind Order and Symphony).
The main castle is easily top 2 in the series for me, really fun to explore — unlike certain games (̶ b̶o̶r̶e̶n̶e̶s̶s̶ ̶o̶f̶ ̶t̶h̶e̶ ̶M̶o̶o̶n̶).
The painting mechanic is really fun, basically a new map in each one.

Speaking of paintings, I think it suffers from the same issue as Order: after fighting the twin sisters, you unlock four more paintings that are basically the same thing. That’s the only boring part for me, but in this case the score goes down more because the game is longer than Order.

Fighting Richter to unlock the power of the Vampire Killer was something I didn’t expect, I thought it was really innovative — but man, the damage was insanely high! Honestly, he was the boss I struggled with the most.
I’d give it a solid 9/10, it was really worth it. The bonus mode with Richter is also pretty fun, you can beat it in an hour and a half at most.

Moving on to Dawn of Sorrow...
I expected more. The beginning of the game was really fun, up until around the second or third boss.
The characters are good and the plot is enjoyable.
The soundtrack is relatively good, with songs like Dracula’s Tears.
The magic seal system is cool at first, but later on you realize it’s not such a really cool thing.
The bonus mode with alucard/julius and yoko is the best in this collection

The soul system is really annoying. You need them to upgrade weapons, some with only a 3% chance of dropping, others from enemies that are a pain to fight — and MANY souls are completely useless.
There’s a part in the game where you need three souls to proceed. Didn’t get them? You have to backtrack through a boring path to the warp room, farm enemies with 2% or 3% drop chance, go back to the warp, take another long route... and only then continue.

Most of the bosses are boring.
The castle is also pretty bad, though not as bad as Circle of the Moon.
The final stretch leading up to the last two bosses is a nightmare, really annoying.

In short, its predecessor Aria of Sorrow is better, but not by much
both are pretty tedious.
I’d give it a 6/10.