For many fans of the Castlevania series, Symphony of the Night was the high point of the series. It's heady mix of music, graphics, and game play mixed with a "new" (if we conveniently ignore Castlevania II) play style liberally borrowed from Metroid crafted something more than the sum of its parts. It was a game in the Castlevania unlike (and, for the most part, better than) anything that had come before it (sorry Castlevania II).
For the years afterwards, though, Konami seemed to have problems giving fans of Symphony the follow up they wanted. Circle of the Moon and Harmony of Dissonance each had their fans, but neither game managed to coalesce the entire fandom behind it the way Symphony had managed to. That changed, though, with Aria of Sorrow.
Aria presented the story of Soma Cruz. Set in 2035 AD, the story concerns Soma as he's mysteriously transported to Dracula's castle. He's not sure why he's there or what's going on, but he feels a dark power growing within him and, on the advice of a mysterious stranger, goes off to explore the castle to find a way out. Like the previous Metroidvania entries, Soma explores the whole castle, moving back and forth, collecting powerups and new abilities all with the goal of completing the castle and ending his tenure in the castle.
What Aria managed to get right was that it was engaging. Gone were the long, sometimes repetative hallways of Circle and the flat, muddy, listless graphics and game play of Harmony. Instead, the game was light, fast, and colorful, with an interesting game play mechanic (the soul collection system) to boot.
While not as "perfect" a game as Symphony, Aria proved to be the game many Castlevania fans had been waiting for.