The best sidescrolling series ever. This game proves you don't need 32 km of viewing distance and radioactive HDR on the real-time foilage to be fun. This series revolves around a vampire hunter defeating dracula. That's the basic premise, you go through Dracula's castle fighting zombies and creatures and all types of badass monsters. Tight control, badass weapons, deep gameplay with awesome moves, kickass sprite animations, one of the best soundtracks in videogame history. All of the games in this series kickass(excluding the dogshit 3D ones which have no right to bear the name Castlevania and Castlevania 2).
Some other series match it such as Super Mario Bros.
, but this game is the epitomy of what makes a videogame good.
My favorite one is Castlevania: Circle of the Moon on the gameboy advance.