Castlevania: Aria of Sorrow changed Metroidvania for the better. The whole series was flipped upside down. The game is set in 2035 (most games are at least before 1800), , and you play as the Japanese teenager Soma Cruz not a European Belmont. You also don't even use whips. Swords are the main weapon in this vania.
I also loved the art style and the story. Finding out Soma's hidden secret (even to himself) was shocking, and pretty mind blowing for the time.
Aria of Sorrow was all about the Soul System, the game's gimmick of a magic system unique to every Metroidvania. Every time you kill an enemy, there's usually the random chance of capturing their soul. Once the soul is caputred, you gain their ability. Works with bosses too. Kinda pokemon meets kirby. Really cool.
Though the game was a tad too short, I loved every minute of it. The boss fights were epic, and I was begging for more by the end of the game. The final boss was kinda shitty I admit. Check out Dawn of Sorrow which is the better of the two.