Kristin Thompson and David Bordwell provide a fantastic dissection of why comic book movies are so damn popular these days:
Not all genres are created equal, and they rise or fall in status. As the Western and the musical fell in the 1970s, the urban crime film, horror, and science-fiction rose. For a long time, it would be unthinkable for an A-list director to do a horror or science-fiction movie, but that changed after Polanski, Kubrick, Ridley Scott, et al. gave those genres a fresh luster just by their participation. More recently, I argue in The Way Hollywood Tells It, the fantasy film arrived as a respectable genre, as measured by box-office receipts, critical respect, and awards. It seems that the sword-and-sorcery movie reached its full rehabilitation when The Lord of the Rings: The Return of the King scored its eleven Academy Awards.Read the rest here.
The comic-book movie has had a longer slog from the B- and sub-B-regions. Superman, Flash Gordon, and Dick Tracy were all fodder for serials and low-budget fare. Prince Valiant (1954) was the only comics-derived movie of any standing in the 1950s, as I recall, and you can argue that it fitted into a cycle of widescreen costume pictures. (Though it looks like a pretty camp undertaking today.) Much later came revivals of the two most popular superheroes, Superman (1978) and Batman (1989).
The success of the Batman film, which was carefully orchestrated by Warners and its DC comics subsidiary, can be seen as preparing the grounds for today's superhero franchises. The idea was to avoid simply reiterating a series, as the Superman movie did, or mocking it, as the Batman TV show did. The purpose was to "reimagine" the series, to "reboot" it as we now say, the way Frank Miller's The Dark Knight Returns re-launched the Batman comic. Rebooting modernizes the mythos by reinterpreting it in a thematically serious and graphically daring way.