I wouldn't say that I'm overly enthusiastic about live-action video game adaptations, and I actually do have a fair amount of trepidation about them given their track record.
However, I do think that Mega Man is a video game franchise with the potential for being a decent live-action film. (Not as much potential as The Legend of Zelda, but potential nonetheless.) I cited the Wachowskis' Speed Racer as an example of a vibrant, kinetic live-action anime--but I'll cite an even better example: think Astro Boy meets I, Robot.
Plot wise, I'm very roughly and vaguely picturing a film that begins by showing how Drs. Light and Wiley worked together to produce a revolution in robotics and artificial intelligence for the general betterment of mankind. Together, they have created a massive corporate robotics monopoly with products as ubiquitous as Microsoft's Windows OS. Rock would be presented as a unique model, the epitome of artificial intelligence as Dr. Light's Astro Boy. We would see Wiley have some sort of a downfall in which he degenerates from a figure not unlike Dr. Light into the mad scientist villain, perhaps with some inciting incident in which he is ostracized. Wiley would seek revenge using a backdoor he programmed into all of their robots from a certain point onward to usurp their control. Rock is free of this backdoor, and as an act of heroic nobility offers to be upgraded into Mega Man to quench this robotic uprising. This last act of the film would be a fairly kinetic action film in which Mega Man fights his way through Wiley's robots to reach him and somehow convince him to end the robotic rebellion. There's enough material there that a halfway-decent script writer should be able to craft an at least passable three act popcorn summer flick.
I would imagine that such a film would aim for the coveted PG-13 rating, and would be marketed to a broad audience spanning young children unfamiliar with the franchise to nostalgic adults who grew up with the property. Speaking strictly in the financial terms of box office returns (and not cinematic quality as art): this approach has worked exceedingly well for the recent Transformers, Teenage Mutant Ninja Turtles, and G.I. Joe films--although it failed in the case of the RoboCop reboot. I would imagine that this movie would seek a Marvel-esque tone that very carefully balances action, drama, and comedy.
As for appearance and style: using superhero films as a barometer, it seems that over the past fifteen or so years Hollywood is gradually getting better at presenting aesthetics that match the source material without being too unrealistic and cartoony. (Although sometimes they go too far and go too grim-dark, which works well for something like Batman or Judge Dredd but would not work at all for something like Mega Man!)
I'm not expecting great art from a live-action Mega Man movie, but I would cross my fingers in the hope for a decent popcorn summer flick (one hopefully better than some of the other films I mentioned above, especially those involving Michael Bay). I have my trepidation going into a live-action video game adaptation, but Mega Man is a franchise that I'm willing to give a chance.