Since Mega Man was so successful on the NES, it's unsurprising that he made the leap over to the Game Boy, too.
There were five Mega Man games in total, but this first one is probably the weakest of the bunch. It offers a measly four bosses (compared to the eight you usually get in Mega Man games), then when you defeat those you get the final Dr Wily stages, where you meet another four.
These bosses are a selection from the first two Mega Man games, so if you've played those you'll be a tad underwhelmed.
Mega Man's famous difficulty remains, but when the game's this short it's really for completists only. Wait for the other four much better Game Boy entries.