The final Mega Man game on the Nintendo Game Boy was Capcom‘s 1994 release Mega Man V, and it is arguably the best in the series.
It was the only Game Boy Mega Man game that had colour capabilities (when you plugged the cartridge into a Game Boy Color), which obviously enhances the graphics. The screenshots here are of the enhanced version.
Gameplay-wise Mega Man V is just as frustrating/compelling/enjoyable as before, but this time benefiting from all the technical knowledge learned from previous games.
The developers throw every Mega Man trick in the book at you, from crushing ceilings to waterfalls that sweep you away – and they also manage to introduce a few new ideas into the mix too. Like, for example, the new ‘Buster’ arm cannon, which comes back to you when fired – a significant addition to the gameplay.
Mega Man V is a tour de force of survival platforming and a handheld gaming classic!
More: Mega Man V on Wikipedia