Hollywood is notorious for its slavish devotion to youth, but leading men who became famous four decades ago are still stealing scenes.

Superstars like Al Pacino, 62, Robert De Niro, 58, Jack Nicholson, 65, and Harrison Ford, 59, are burning as bright as ever.

"They're still as valuable now as they were 25 years ago," said Marcia Ross, senior vice president of casting for Disney/Buena Vista Pictures.

"Someone like Gene Hackman [72] will work as long as he wants," she said. "It will be a sad day when Gene Hackman decides to stop making movies."

Susannah Gora, associate editor of Premiere magazine said that for men unlike for women age can work in their favor.

"There are a lot of men who get sexier with age," said Gora, who just saw Ford's new movie K-19: The Widow Maker. "Harrison Ford will be a sex symbol for a long time. In K-19, he's virile, he's strong, he's sexy, he doesn't seem like an old man."

Still, it's impossible to see Ben Affleck, 30, assume the Jack Ryan role in this summer's Sum of All Fears and not sense a torch being passed. Ford played the character in two earlier films in the series.

Apples to Oranges?

The new generation of stars can bring in audiences, but do they have what it takes to fill the shoes of those who came before them? Consider the early careers of the last generation.

By the time he was 40, De Niro had made Taxi Driver, The Deer Hunter, Raging Bull, and The Godfather II; Dustin Hoffman had made The Graduate, Midnight Cowboy and Lenny; Pacino had made both Godfathers, Serpico and Dog Day Afternoon; Robert Redford had made such classics as Butch Cassidy and the Sundance Kid, The Sting, The Way We Were, and All The President's Men.

But will a next generation actor like Brad Pitt, 39, live up to the often-made comparison with Redford? While his resume is slightly less impressive, it reflects modern critical and box-office hits such as Seven, A River Runs Through It, Fight Club, and Twelve Monkeys, for which he was nominated for an Oscar.

Industry observers say they don't put much stock in such Pitt/Redford comparisons and point out that today's movie biz is much different than it was when films like Taxi Driver and Midnight Cowboy were being made.

"I don't know if we have the roles that Hoffman and Pacino took in their thirties. We might not make those films anymore," said David Irving, a film studies professor at New York University.

And Hollywood is not experiencing a shortage of talent in its younger stars, according to experts.

Actors like Tom Hanks, 46, Russel Crowe, 38, Sean Penn, 40, and Denzel Washington, 47, have amassed impressive bodies of work. And younger actors like Affleck, Matt Damon, 32, Pitt, and Edward Norton, 33, are rapidly fleshing out their resumes, Ross said.

Sleeping Giants

But what about actors like Kevin Costner, Alec Baldwin, Ray Liotta, and Dennis Quaid? All in their mid-40s, these once-promising stars seem to have fallen off Hollywood's A-list.

Not so, said Ross. A movie star is a movie star. Once you've got name recognition, you can come back any time. Ross calls this the "Richard Gere Syndrome."

"Richard Gere has had a remarkable career," Ross said. "He comes and goes. He's a star, whether he's in hot movies or not," she said.

The poster boy for this syndrome, of course, is John Travolta, whose name is invoked almost reverentially as proof anyone can come back. For example, Dennis Quaid just had a huge hit in The Rookie and is now being offered "tons of stuff," Ross said.

"Any actor can make a shift at any time," Irving said. "Actors like Dennis Quaid and Jeff Bridges are solid, strong actors. In the right role, they're just amazing."

Ross said that 20 years from now we'll be having the same conversation about most of today's younger actors. "I really think that when people are really talented, their age becomes secondary," she said.