Irem themselves developed and published this 1990 handheld, monochrome remake of the classic Kung-Fu Master, and it is not too bad, all things considered.
Game Name, System (Release Date)
Mega Man, Famicom (17th Dec 1987)
Mega Man 2, Famicom (24th Dec 1988)
Mega Man 3, Famicom (28th Sept 1990)
Mega Man: Dr. Wily’s Revenge, Game Boy (26th July 1991)
Mega Man 4, Famicom (6th Dec 1991)
Mega Man II, Game Boy (20th Dec 1991)
Mega Man 5, Famicom (4th Dec 1992)
Mega Man III, Game Boy (11th Dec 1992)
Mega Man IV, Game Boy (29th Oct 1993)
Mega Man 6, Famicom (5th Nov 1993)
Mega Man X, SNES (17th Dec 1993)
Mega Man V, Game Boy (22nd July 1994)
Mega Man X2, SNES (16th Dec 1994)
Mega Man 7, SNES (24th March 1995)
Mega Man X3, SNES (1st Dec 1995)
Mega Man 8, PlayStation (17th Dec 1996)
Mega Man X4, PlayStation (1st Aug 1997)
Mega Man X5, PlayStation (30th Nov 2000)
Mega Man X6, PlayStation (29th Nov 2001)
Mega Man Zero, Game Boy Advance (26th April 2002)
Mega Man Zero 2, Game Boy Advance (2nd May 2003)
Mega Man X7, PlayStation 2 (17th July 2003)
Mega Man Zero 3, Game Boy Advance (23rd April 2004)
Mega Man X: Command Mission, GameCube (29th July 2004)
Mega Man X9, PlayStation 2 (7th Dec 2004)
Mega Man Zero 4, Game Boy Advance (21st April 2005)
Mega Man ZX, Nintendo DS (6th July 2006)
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.
The fourth Game Boy Mega Man game – Mega Man IV – was published by Capcom in 1993 and continues the tradition of this tough, but highly playable, run and gun series.
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.
In essence: a cut-down version of the first Mega Man game, but with graphics made to fit the monochromatic Game Boy. First published in 1991 by Capcom.