Castlevania: Dawn of Sorrow is one of the best in the series and the game works incredibly well in the dual screen DS set up.
Ever since the Castlevania series was revolutionized by Symphony of the Night for the PS1 the portable versions have followed suit with this "Metroid-vania" type game. The 2D platformer style where there's a map with save points as you traverse the castle simply works very well. There were 3 GBA titles that followed this same formula and were generally well received and successful.
Dawn of Sorrow follows the same formula as these predecessors. But, since it's for the Nintendo DS there's an added advantage with the 2nd screen. This allows for one of the screens as a dedicated map for referencing and it works perfectly. The ability to avoid pausing to look...