This will always remain to be an important game. It's really hard to see especially nowadays how much of a revolution this game was, but in 1986 game design elements that we deem obvious weren't so much the case back in those days. Compared to most games released in this era that would often have brutal beginnings, in Castlevania, everyone can beat the first level. It's a wonder of level design, you start off in the garden without any enemies, hitting pots that drop hearts. Your first moment in this game is spent getting accustomed to the controls without having an annoying text telling you what to do.
While yes, like most NES game, Castlevania show its age, I still believe it is very interesting to experience a game that has marked the gaming industry, just to see at the very least where it all started.