Pundits who thought the strike would cripple Leno misunderstood something fundamental about his art: His act is already essentially crippled. (…) A monologue is, by definition, wounded comedy. We should assess late-night hosts, then, not by their rare bursts of excellence but by how they cope with mediocrity.
Letterman seems to loathe his monologue. (…)
Leno, on the other hand, is a realist. He doesn’t pretend to be better than his material or his audience. He’s a virtuoso of the mediocre, resigned to the staggering failure rate of late-night comedy and proud of whatever success he manages to bring off. Unlike Letterman, he tells his jokes straight, with the implication that they are actually funny and worthwhile. His only protective mechanism is his legendary work ethic: Since striving for quality in a late-night monologue is hopeless, he invests all his talent in quantity. This is the secret of Leno’s success: He’s not trying to be the funniest guy in the world; he’s trying to be the most dependably serviceable at monologuing—an equally difficult task that carries almost none of the turkey-cocking street cred of revolutionary art comedy.
Very well written article from Sam Anderson at NY Mag about why Leno continues to be more popular than ever.