Human nature craves legends of larger then life heroes to capture their imaginations. Gilgamesh, Hercules, Sampson, Achilles, and many others had super human abilities, and have legends that have lasted thousands of years. The superhero comics may have gone into steep decline post WWII, but they never died. Superman was must see TV for a generation of kids. Even adults complained that they wanted to see the movie serial Superman fly, but they had to wait till George Reeves flew over the Warner Brothers Studio. Batman, Captain Marvel, the Phantom, Zorro, and Tarzan all made it onto both the big, and little screen.
When I was a kid we all loved Batman, even though at 7 I knew it was campy. My father would watch with my brother, and me, and get a laugh out of it. I remember my dad shouting to my mother. "Hey mommy, get a load of the Catwoman." Yea, Julie Newmar was amazing. What young man doesn't remember Linda Carter, as Wonder Woman? Then we all believed a man could fly. We also had endless cartoons, with heroes of every description, who could fly, had super strength, super technology, and were all brave, and noble.
So even as the media of Comics have had low sales for generations, movies, TV, toys, and action figures were where the money was made. Someone may never have read the Justice League, but who never saw the Super friends? Most people know the X-Men from Cartoons, and movies, not from reading comics. When the Marvel Movies started most people had no idea who Ironman, or Thor were. So I think the movies, and TV would be where new super legends would be born.