Superman just entered his 75th year, but he has always been ageless as well as timeless. In the 1930s, he was just the crime-fighter we needed to take on Al Capone and the robber barons. In the '40s, he defended the home front while brave GIs battled overseas. Early in the Cold War, he stood up taller than ever for his adopted country, while in its waning days, he tried to eliminate nuclear stockpiles single-handedly.

Over the decades, the Man of Steel has evolved more than the fruit fly. For each era, he zeroed in on the threats that scared us most, using powers that grew or diminished depending on the need — as did his spectacles, his hairstyle, and even his job title. Each change took the pulse of the nation and its dreams. Each generation got the Superman it needed and deserved.

So what about now, when our teetering economy, overseas entanglements, and political vitriol leave us craving a hero as much as we ever have?

Some say what we need is an avenger, which would explain the roaring success of the recent Marvel Studios movie The Avengers. Others insist we need a Dark Knight like Batman or a fraught champion like Spider-Man, both of whom are launching their own big-budget movies.

I say balderdash. Vengeance and darkness are precisely what we are trying to escape. The superhero for our age has to be a beacon of light, and none shines as bright as the Last Son of Krypton.

Superman's irresistible allure lies partly in his powers: the strength to lift boulders and planets, the speed to outrun a locomotive or a bullet, and the gift that tops countless wish lists: flight. There's also the seduction of the love triangle of Clark Kent, Lois Lane, and Superman, which has a side for everyone — whether you're the boy who can't get the girl, the girl pursued by the wrong boy, or the conflicted hero. And Superman is forever 29 years old, which lets us feel like we're 10 again.

So what if the upshot of his adventures is as predictable as those of Sherlock Holmes? It's reassuring that the good guy never loses. His uniform of tights and cape in radiant primary colors makes Superman as instantly recognizable as Santa Claus — and as comforting.

That has helped Superman's handlers keep him relevant for nearly three-quarters of a century and counting, moving him from print to the airwaves, from small screen to big. There was never a need to explain who he was; everyone knew as soon as they saw him. His endurance made him the envy of mortal heroes like Jack Kennedy, Joltin' Joe DiMaggio, Batman, and Jerry Seinfeld, all of whom were inspired by him.

But there is one more factor that explains Superman's lasting appeal: his crystal-clear sense of right and wrong. Like James Bond, he sweeps in to solve our problems — no thank-you needed. Like Jesus, he descended from the heavens to help us discover our humanity. And he does it all, as we are reminded in the recently released animated film Superman vs. The Elite, while staying true to the ethical guideposts that have defined him since Jerry Siegel and Joe Shuster dreamed him up in the '30s: no killing, even when the victim deserves to die; no forgetting that means are as important as ends, no matter how clunky that concept sometimes seems; no wavering from protecting the 99 percent, however tempted by the benighted 1 percent.

The more flesh-and-blood role models let us down, the more we turn to fictional ones who stay true. With them, and especially with Superman, it is about the possibility — of getting the girl, saving the world (or at least Lois and Jimmy), and having it our way. Our longest-lasting hero will endure as long as we need a champion, which should be until the end of time.

Larry Tye is the author of "Superman: The High-Flying History of America's Most Enduring Hero," published last month by Random House.