I remember playing the original Cave Story when the fan-translation by Aeon Genesis hit the net and it’s easy to see why it became such a hit in the indie space before that was even a thing. A pretty big, highly polished platformer with a big, semi-continuous world, charming visuals and highly compelling platformer gameplay.
These days I mostly get annoyed when another Top-10-Metroidvania-Games-List lists Cave Story among them, as the game in theory has one large, open world ready to explore, but the narrative effectively forces you along a very linear, highly gated path that doesn’t allow much freedom to explore. More or less adventure elements grafted onto an excellent platformer (a long and veritable tradition in games), but not a metroidvania game.
That said, I never get annoyed at the game itself and replaying the commercial plus-version brought home just why. The distinct upgrade mechanic for weapons, the enemy design and the excellent boss fights, the overall great level design, the cute characters and engaging story, the difficulty that slowly ramps up from easy to average to hard to hell no. The game has it all and then some.
The added gameplay modes for the plus-version and the various technical improvements (higher resolution, optional soundtracks) are nice-to-haves, but if all you want to do is play the game, the free option is still available and has exactly the same brilliant gameplay as the game you pay for. Overall, whatever version, it’s a great game.