Even with the American tweaks that make it way too frickin' hard, Castlevania III is a real banger. Play the Famicom version for a slapper of a soundtrack taking advantage of a special sound-chip, as well as a more forgiving (but still tough!) difficulty.
Castlevania III takes the already basically perfectly executed Castlevania 1 (in my heavily biased opinion) and improves on it in basically every way. More levels, better graphics, more characters, better music, better overall structure and challenge, some path choosing for replayability.... this game is amazing. It's a strong vote for the NES game to play if you can only play one in your entire life, in my opinion. It's got everything.
5 - Masterpiece: Either a personal favorite or so good I can't deny it a 5
Castlevania III takes the already basically perfectly executed Castlevania 1 (in my heavily biased opinion) and improves on it in basically every way. More levels, better graphics, more characters, better music, better overall structure and challenge, some path choosing for replayability.... this game is amazing. It's a strong vote for the NES game to play if you can only play one in your entire life, in my opinion. It's got everything.
5 - Masterpiece: Either a personal favorite or so good I can't deny it a 5