Among the latest crop of male stars, many, like DiCaprio and LaBeouf, established themselves at a young age, which is part of the reason they have a hard time leaving their boyish personas behind.
Goodwin said these younger men are also more marketable, since they can appeal to both audiences in their 20s and teens.
Hollywood has also been more willing to cast a nontraditional leading man since putting Keanu Reeves in the "Matrix" franchise. "Keanu was kind of a transitional figure," Kilday said.
Goodwin agrees that studios are more open to other options if they can't find that traditional man's man. "It's opened up the doors for actors who haven't seen themselves as castable for a role because they didn't necessarily fit the physical type."
Gehring adds that it's also a lot easier for leading men such as Clooney, Pitt and DiCaprio to play against type than it was during Hollywood's golden age. Actors from an earlier era, like Robert Redford and Harrison Ford, generally stick close to the leading man type. Otherwise, if they divert from it, like Ford did in "What Lies Beneath," where he played a murdering cheating spouse, they draw flak.
But someone like Josh Brolin can play the nasty cop in "American Gangster," the sympathetic everyman in "No Country for Old Men" and a satire of President Bush in the upcoming "W."
"The difference I see," said Gehring, "is the tendency for the more contemporary leading man to play a variety of parts."