Mr. Spook wrote:
George Clooney, the quintessential movie star today, was a regular on The Facts of Life and a hit on E.R. Was HE a "TV actor"? What changed about his work that altered his status?
He no longer does TV.
Remember when Robin Williams did a guest spot on Homocide? Sure, he was Mork, but he let that stuff go long ago. It's generally expected that when an actor graduates to movies that they will avoid TV work afterwards.
Johnny Depp for instance, got his start on 21 Jump Street. But after he left TV, he never came back, and probably never will.
The newest guy to rise up is Joseph Gordon-Levitt. He was on 3rd Rock from the Sun. Now he does A-list dramatic turns and will probably not do much TV going forward.
Your cache as a film actor has to do with limiting your exposure. Sure, there's always reruns of your prior work, but you want people to have to go to the movies to see you each time, not tune in each week. Shatner was doing TJ Hooker at the same time as a couple of the films. But that was because Shatner never made a huge impact on the film industry aside from Star Trek. Most of his films other than Trek are light comedies like Airplane II.
I'm not making a value judgment on how good I think these actors are, just that there's a difference in how the public sees a 'star' whether they are on TV or movies. Actors who are top box office stars or regular oscar contenders stay away from TV.