System: Famicom (Japanese NES)
During the height of the Mega Man series' popularity, Capcom of Japan released Rockboard for the Famicom - a board game based loosely on the Mega Man theme, containing lots of different minigames. The end result and overall goal of the game? To stop Dr. Wily from taking over the world with his army of robots. Since the title never came to the US, most people aren't aware it ever existed - and it's not of particular interest to anyone but Rockman fans.
System: Game Boy
The Mega Man series for the Game Boy, known as the "Rockman World" series in Japan, saw Capcom taking half the bosses from one NES game, half the bosses from another, and then sticking them into a black-and-white world and calling it a new game. The first game, for example, featured Elec Man, Cut Man, Ice Man, Fire Man (from the first Mega Man) Bubble Man, Heat Man, Flash Man, and Quick Man from Mega Man 2. The gameplay did its best to faithfully mimic the NES versions. Finally, with Mega Man V for the GB, the designers got original - it featured planetary bosses: Mercury, Neptune, Mars, Venus, Terra, Pluto, Uranus, Jupiter, and Saturn. It also featured the original helper Tango the Cat, who served a similar function to Beat in providing much destruction. The third through fifth games in the series are rare finds, but the first and second have been reissued in a bargain series and are now quite common.
System: Game Gear
US Gold - the publisher that formed half of the marriage that became Eidos - wanted a slice of Mega Action on the now-discontinued Game Gear console, so it sublicensed the series from Capcom. The resulting game is a hybrid of the NES Mega Man IV and V. Developed by Freestyle, not Capcom, the game features an extremely abbreviated version of Mega Man IV's intro and levels, as well as the bosses. Bright Man, Toad Man, Stone Man, Napalm Man, Star Man, and Wave Man. It's a decent, if somewhat sluggish, translation of the Mega Man series - and the one of the few color portable versions available.
Before Capcom started publishing its own PC games (about the time that Mega Man III was out for the NES), a now-defunct company known as Hi-Tech Expressions licensed the title from Capcom and developed three totally horrible, original DOS games. These games you most definitely do not want to play - the control and graphics are abysmal. Still, for the sake of completeness, they must be included in this retrospective.