Fair point regarding comparisons, but even if you ignore that the early Superman movies were made by a different studio. . . they were still 30 years ago. That long a time is such that you can't really draw much of anything useful from their existence, because the people at DC are different, the people at all the movie studios are different, the audience is different. . . there is basically no continuity.
Whereas, by contrast, there is a common creative cadre at Marvel Studios that bears continuity from Iron Man to the present. There's also a similar creative cadre at WB surrounding Chris Nolan. Likewise at Sony and Fox, to varying extents ( though I suspect there is very little of it, re: the Spider-man franchise by now ). Even in those cases, though, at least your talking about an audience that is a lot more similar to the one of now, then the audience of 1979.