It's not just super hero movies, it's a multitude of factors. Geeky stuff has been more and more cool (or at least less socially unacceptable) over the last 20 years. I think Buffy might have kicked it off, and we had the massive Lord of the Rings movies making Orcs and Wizards OK (it's easy to forget now how huge these movies were), more recently Game of Thrones being the biggest TV show, etc. The parallel rise of video gaming (widening its demographic), plays a part, too, as of course does the Internet, which allows awareness of geeky things to spread, and in a positive way (not the old "ban it, they're trying to summon demons" publicity from the 80s). Or look at MMORPGs, taking concepts like hit points from pen-and-paper games, but then providing a new generation of players for tabletop RPGs, and influencing, tabletop design. Plus you've got the explosion in creativity and production values in board games, which has been steadily building on the success of Eurogame designs from the 90s.
I'd say that superhero movies have benefited from all that as much as tabletop games have, although it reaches a point where everything feeds everything else.
