More than the suit has made its way into pop culture. Without Superman, would we refer to rivals or weaknesses in terms of "kryptonite," that Superman-stifling substance? Would really smart people be referred to as "brainiacs," after one of his nemeses? Would we wonder about "bizarro world"? Would such catchphrases as "faster than a speeding bullet," "up, up and away" and "this is a job for Superman" have ever been uttered?
Some of those details came from the inevitable spinoffs of the character -- movie serials, television shows, a mid-'60s Broadway musical (with a book by Robert Benton and David Newman, who later co-wrote the script to the 1978 movie), Saturday morning cartoons and, of course, the major motion pictures.
But somewhere along the way, the character also became a bit of a joke -- too perfect, too earnest, too much of a good thing. His writers didn't help, giving him new powers when they needed to finesse a plot -- and taking them away when it seemed he'd gotten too god-like.
Author Larry Niven, wittily taking Superman's powers seriously, even wrote a story in the early '70s about what would happen scientifically if Superman ever procreated with an Earth woman. The result, Niven believed, could be messy: the title was "Man of Steel, Woman of Kleenex."
He lost touch with the real world -- or, perhaps, the real world lost touch with him. "Superman never made any money / For saving the world from Solomon Grundy / And sometimes I despair the world will never see another man like him," lamented the Crash Test Dummies in "Superman's Song."
"Superman predates the Cold War, but he really is a Cold War figure, because he fights evil without shading and without nuance," says Jerald Podair, an American studies professor at Lawrence University in Wisconsin. "Once the idea of evil becomes more complicated -- once quotation marks are put around it -- that's a problem. He's too black and white in a morally gray environment."
Yet Superman abides.
"One of Superman's editors was quoted as saying, 'He's invulnerable. Even bad scripts can't hurt him.' And there were years when it looked like they were testing that theory," Evanier says. "There have been long stretches of time when people bought Superman in spite of the comic book, not because of it, because they just liked the fantasy. They liked the character."
Even as his comic-book sales have waned -- and, frankly, comic-book sales have waned in general -- he's never gone away. Jerry Seinfeld, a huge fan, dropped Superman references into his sitcom, and later co-starred in a series of commercials with the character. Children still leap through gardens wearing capes, and adults are proud to don outfits with the famous "S."
"Superman inspires me and many others because I feel he represents the good in all of us," superfan Robert Levine told CNN iReport. He wore a Superman cape at his 2011 wedding. "He has always been the king daddy."
The character can still bring a pretty penny on the market as well, particularly works from his early years, says Heritage Auctions comics expert David Tosh. Action Comics No. 1 -- the superhero's introduction -- is still "the holy grail" of comic books, he says. One copy sold for more than $2 million in 2011. Tosh estimates the "Mile High" copy, which was part of a collection owned by collector Edgar Church, could go for more than $5 million if it ever goes up for sale.
Still, he says, today's Superman just doesn't have the same value. Even with all the changes DC has made over the years -- the mid-'80s Crisis on Infinite Earths series, which attempted to straighten out continuity issues; the character's 1992 death (he wasn't quite dead, of course) -- haven't managed to push the character to the popularity levels of the angst-ridden Batman or Marvel universe heroes like the Avengers.
"They've rebooted the Superman character a number of times now and it always has a brief period of heightened interest, but it'll never be the same as it once was," says Tosh.
Could new angles change Superman's fortunes? An emphasis on his status as an immigrant, which would bring him into a contentious 21st-century political debate? More anger than sorrow at injustice? (The early Superman, writer Arie Kaplan notes, wasn't as pleasant, but more of a "cocky daredevil.") Greater cyber-abilities, less dependence on muscle? (He is a trained journalist, though he quit the Daily Planet last year.)
The new film attempts some alterations in tone, as is expected in the age of "The Dark Knight" and Robert Downey Jr.'s "Iron Man." But whenever changes are made, there's always the wrath of the fans.
"I think about the fan uproar when they revealed Superman's new costume, and he didn't have the red underpants," says Paul Booth, a pop culture professor at DePaul University.
You just don't want to fool with the Man of Steel.
Maybe he's not the trendy thing. Maybe there's too much competition in the superhero arena. But, three-quarters of a century after his creation, his impact -- and his values -- remain timeless.
"You're very conscious of the history of this and the fact that you're a link in the chain," says Kaplan. "It becomes more apparent when you're writing these stories what a debt the industry owes to that character.
"I've written a lot of classic characters," he adds. "But when you write, 'Exterior: Metropolis street, day, Superman flying above the street,' you turn into an 8-year-old fanboy again."