For me it's Ludovania: Dracula X. It combines the expanded moveset and combat focus of Rondo with level design and challenge close to the NES games (3 especially), and recontextualizes many elements of Rondo in new and creatives ways, like using the key to free Maria turned into a relentless gauntlet across an entire stage.

Ludovania Dracula X > everything else

Only CV3 comes close