Hard to answer this. Three awesome games. I like all of the three very much. They are close together for me when I have to rate them. All of them have a lot of good Castlevania music and I can listen to that for hours.
Portrait of Ruin: Two protagonists at once is a great idea. Unfortunately this game mechanics are unbalanced. The super attacks just slaughter everything without any effort (so does the subweapon "Shuriken" when mastered). There is simply no difficulty at all until you reach Dracula (and the Nest of Evil). Since I want a challenge when playing a game this one comes last for me.
Dawn of Sorrow: Frustrating soul collecting – having to harvest multiple of very rare drops to max out attacks and use souls for forging weapons. No cheap spamming the bosses with super attacks in this title – though the overall difficulty is pretty low and a small amount of grinding can help anybody to overcome obstacles.
About the "draw a magic circle" touch part: I've seen people expressing extreme hate about this. Never understood this. Did I like it? No. Did I care? Not really. It's not permanent forced touch controls like the DS Zelda games or Star Fox or anything like this. Two seconds drawing some lines… and done.
Order of Ecclesia: Most convincing in the graphics department and the difficulty is higher than on the previous titles. Grinding will not help much if you don't practice hard enemies or bosses. I've yet to play hard mode with Lv.1 cap. This will be brutal. The variety of locations (not only the castle), the difficulty and Shanoa are reason enough to give it first place.
============
I really miss classic 2D Castlevania titles, both the simple linear and the Metroidvania style games. My dream would be a modern HD version all from Castlevania I to Order of Ecclesia in one collection with a button assigned to seamlessly switch between classic look, sound and feel and modern HD (This is so well done on "Day of the Tentacle – Remastered")
Edit:
I forgot to mention this. Those game have become so expensive and hard to get! I bought them for about 10 Euros each when they were almost new. Nobody seemed to want them. Especially Dawn of Sorrow was everywhere, sometimes for less than €5.
