Castlevania

Dawn of Sorrow, Portrait of Ruin, and Order of Ecclesia were the only games for DS. They're all great, but to me Dawn of Sorrow will always be the best. It was the first for the handheld and employed such a cool system of useable "soul collecting," very similar to collecting familiars in MapleStory. Other little touches were great too, like the creepy originality of the game, and the Magic Seals upon defeating each boss, which required use of the stylus to complete.

I've only played the GBA game that DoS follows, but I wasn't a big fan of how you have to go into the menu to select the right soul for the situation. Constantly switching on every other screen got really tiresome. Did they improve that on the DS?

Also, the unique, hidden monsters not having guaranteed drops was a pain in the ass. Basically had to farm for the soul by resetting the map over and over again.