Having always been a fan of monsters and spooky things in general, as well as the action genre, this game holds a special place in my heart. It was the game that really made me an obsessive fan of the Castlevania series, which I believe to be one of the richest, coolest, and overall best quality game series out there. Some of the things that make this entry in the series stand out:
-it introduced Trevor Belmont, the famous Simon Belmont's ancestor. When the game was released and for many years afterward, Trevor was described as the first Belmont to ever fight Dracula. Eventually the canon introduced Sonia Belmont (in Castlevania Legends) and claimed she was the first, but most recently Leon Belmont became the end-all official first in the Belmont bloodline to fight Dracula (in Lament of Innocence).
-It introduced three other playable heroes, greatly increasing the game's re-playability. These included the wall-climbing pirate Grant DaNasty, the sorceress Sypha Belnades, and Dracula's own son, Alucard, who eventually became a very popular hero in his own right when he became the protagonist of Symphony of the Night.
-There were several points in the game where your path split, and you had to choose which way to go. This totally changed what levels and bosses you'd encounter on your way to fight the Count, as well as which of the other three heroes you would run into and could then take with you.
-Great music and graphics. Apparently there was a special chip added to the game cartridge to enable even better graphics than the NES was supposed to be capable of.
In short, this game is totally awesome. Even after all the years and all the advances in technology and the many fantastic games that have come out, this remains one of my favorite games ever. Great gameplay, great atmosphere, great action and monsters, etc. A shining moment in the already incredible Castlevania series.