His constant presence in pop culture is so pervasive that it's easy to forget he reached a milestone anniversary this year. One look around San Diego Comic-Con this month, and you'd have spotted the star of the show, continuing to fight for truth, justice and the American way even after 75 years. Superman is here to stay.

"There isn't really a fictional character who has saturated American pop culture like Superman. Sometimes he's in the background and maybe Batman is more popular, but underneath, it's all still about Superman," said Dr. Brad Ricca, author of Super Boys, a biography of his creators, Jerry Siegel and Joe Shuster.

Through multiple panels at the show, itself attended by more than 130,000 comic fans and tradespeople, Superman's past, present, and future were explored in unimaginable detail. His evolution was traced from the earliest days of his creation, by the two Cleveland teenagers in 1938, to contemporary references in Tarantino movies and video games. He's changed over the years, but not as much as others in his genre. And with Man of Steel earning more than $600m at the box office this summer, he's clearly as popular as ever.

This character has become such a part of our culture that you never need to read or see anything with him in it to know the details.

"No one [in the beginning] ever thought anyone over 12 would have an interest in this, and now [Superman] is so central to pop culture. He's everywhere," said Dr. Charles Coletta, a professor of popular culture at Bowling Green State University, who adds that he never has to explain the basics of Superman to his students when the hero is mentioned in classes. Even kids who would never pick up a comic book know all about his backstory.

75 years is a long time for a character to remain relevant. What about this one keeps him around? One attractive aspect of the character is that, despite how much the fine details have changed over the years–the art, the writing, the reboots–his origin story and his uncomplicated fight for justice have resisted modernization.

"At the heart of who he is, it's the ultimate immigrant story and the ultimate American dream…it's really a story that resonates with people," said DC co-publisher Dan DiDio.

Looking at the aspects that have stayed the same, it's clear to see why he's relatable. Who hasn't felt out of place, like they were from another world, and struggled to find themselves and make a difference? It's this struggle that so many people relate to, and it's a reason why Superman's influence has spread through all types of media including radio, video games, movies, TV, music, and books.

"The core of his origin story stays the same. Somebody trying to find himself, trying to find his adventure, and fulfill his potential," said Dr. Andrea Letamendi, a clinical psychologist who has spoken about psychology and comic books at multiple conventions. "The core of the story is still there, which means adapting these other pieces and components can still work, 75 years later, because the origin story is so complete and so relatable."

His biggest impact remains felt in the medium he originated from: comic books. Superman can be considered the first superhero, largely responsible for the whole genre.

"I've spoken with a lot of people over the past week and we agree there wouldn't be a comic-con without Superman," Dr. Ricca said. "There might be movie-con or something around whatever's popular now, but it wouldn't be comic-con. He kick started the whole superhero genre. Every hero has a little bit of Superman in them."

Despite Batman, Spiderman, or other heroes muscling in on his popularity through the years—each with a distinctive original story of their own—there's something special about Superman. In one display at the convention, DC Entertainment arranged Superman's costumes from various movie and TV incarnations over the years. DiDio said it was interesting to see how different costumes attracted different varieties of visitor: attendees were attracted to the garb that represented something specific to themselves.

It's this ability of the character to adapt to each generation, without editing the straightforward core design, that lets him stick around in our culture. During his early, pre-war years, kids wanted to see him handling crime and corruption. During World War II, he took on the Nazis. Nowadays, a more realistic Superman stands up for humanity itself. Fans received a glimpse of this grimmer Superman in Man of Steel, and some were disturbed by the tone. According to comic book writer Grant Morrison, though, the character was reflecting our feelings—just as he's always done. Morrison stressed that we shouldn't forget that Superman still represents the best in all of us, our own struggles to fulfill our potential.

"Right now we're in kind of a dystopian atmosphere in the west," Morrison said on the Superman 75th anniversary panel at comic-con. "Superman's having to reflect that. So I think it's an inevitable part of his development through history. … If he's dark now, it's because we're all a little bit dark."