What Makes it a Mega Man?

Rockman Day Wallpaper showing most incarnations of the series.

Pardon me for the abstract thinking of today's post, but after seeing the latest wallpaper released by Capcom on the fan holiday of Rockman Day (June 9th, see this post by Protodude), I got to thinking about this series in its roots, and in its saturation. 

In a recent presentation, series creator, and former Capcom Keiji Inafune, stated that Capcom had a policy in place setup to reject new Intellectual Properties.  Here's a snippet from Joystiq:

In one anecdote, former Capcom exec Keiji Inafune illustrates how he got so high up in the company and the kind of behavior that likely led to his hasty exit. During a presentation at Kyoto's Ritsumeikan University, the Neptunia Mk-II weapon dished on the corporate culture at Capcom, and how he gamed it to get Lost Planet and Dead Rising made.

Before those games, he said, Capcom had a rule requiring 70-80 percent of the games produced at the company to be sequels, and the management rejected pitches for new titles even beyond that proportion. Inafune started up two new projects, Lost Planet and Dead Rising, and just kept them going even after the prototypes were rejected.  Source Joystiq

Keeping that in mind and seeing all the incarnations of Mega Man as he is today, one has to ask themselves how many of these games would even exists if they did not bare the Mega Man label?  Beyond profit motivations, and references to past games, what ties these games to the Mega Man property?