Capcom blog upon recognizing Mega Man holds the Guiness record for "Most Number of Games In a Single Series," admits that the franchise has been "milked like no other milking in the history of video game milkings!"
The Guinness World Record Gamer's Edition recognizes 46 Mega Man games, but the Capcom blog adds several more that were Japan-only or very much off the beaten path (Mega Man Soccer?). Capcom is actually asking for help in figuring out all the Mega Man games (not counting appearances in other titles). Whoever lists them all on the Capcom site first gets a "semi-official Capcom gold star of complementarianism" and "some kinda random prize." Good luck!