Both Mega Man II and Mega Man III were published in 1992. Capcom was really knocking them out for the Game Boy in the early 1990s.
Again: what you get is a cut-down version of an existing Famicom game (Mega Man 3 specifically). No bad thing when the games are as good as the ones in the Mega Man series. And the gameplay translates perfectly well to the Game Boy, even if you discount the loss in screen size due to the lower resolution.
In this game the themed boss baddies are: Spark Man, Gemini Man, Snake Man, and Shadow Man. All these characters feature in Mega Man 3.
Graphically, I think this third Game Boy Mega Man game is more intricate and darker than the previous two games, which gives it an edge. Gameplay-wise: it’s just as challenging and frustrating as all the others.