I've played through all of the NES, GBA, SNES, Sega Saturn, Playstation Castlevania games (now I've completed the DS games). In my opinion I feel that the game's fundamental side scrolling game mechanics is timeless and in Portrait of Ruin it has already become a perfected art (probably perfected in SoTN). Konami made a wise decision to take out the finicky boss "seal" that was implemented in Dawn of Sorrow and included the bosses from Dawn of Sorrow. Overall, I found this game to be much more difficult than Dawn of Sorrow or some of the contemporary games (GBA especially) because Konami wisely took out the exploit of taping down a button or summoning a familiar to farm experience from infinitely respawning zombies. Some of the things that I miss are the uber-weapons from SoTN such as "vorpal blade" and "rune sword" I know it spoils the game but if it could be included as unlockables after you beat the game that would have been great. I also liked how they reintroduced the special moves system (SoTN; Soul Steal, Dark Metamorphosis, etc) in which a certain button combination (sort of like Street Fighter) could be inputted to perform a special move. Though the moves themselves aren't that great (it's hard to bust a move in a middle of a battle) it's still insanely to fun to beat on enemies that way.
Konami has really out done themselves when it comes to different character modes in Portrait of Ruin. Not only do you get to play with two different characters on the start but you get to play with 3 additional character modes once they're unlocked. Not to mention the boss rush modes is beefier than than Dawn of Sorrow because Portrait of Ruin also includes most of the bosses from Dawn of Sorrow.
I've always thought that some of the previous games suffered to balancing issues and Konami seems to have taken care of that with the increased difficulty and I also thought the new quest system was a really fun way to get stuff and design some peculiar stage sets. The interaction between the NPC and your characters is a lot more dynamic compared to previous games (the NPC merchant actually reacts to your upcoming battle with the last boss).
Final Words: It's a great game and a steal at around 30 dollars.
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