It's a pretty good sidescroller. The controls are responsive, the environments are relatively interesting, and enough variation occurs due to new power-ups to keep things fresh.
If you're worried about the story, this game is technically 2/3 of a trilogy originally planned by Wayforward. The first part was called "Risky's Revenge" and got a lot of complaints for being too short, so they mixed the last two parts into Pirate's Curse. You can find Risky's Revenge on Steam or pirate it somewhere, but remember, it's pretty damn short.
The game's very easy simply because you get a ton of healing items, including one that will immediately resurrect you on death, so don't go in expecting Ghosts 'n Goblins. It doesn't bring anything new to the genre but it does what it does well. Pirate it, buy if you like, enjoy the high-quality art and solid gameplay.