My fav game in the series. For a launch title, this was quite impressive back in the day. It featured some amazing effects never seen in a home console before and stayed loyal to it's roots gameplay wise.
Of the old-style Castlevania's, Castlevania IV is probably my favorite. The graphics, the soundtrack, the gameplay, the level design. Just pure perfection if you ask me.
This game wins eternally for introducing the awesomeness of Slogra and Gaibon.
I liked the fact that it was also the only CV game that enabled you to swing the vampire killer in multiple directions.