For a long time, George Clooney was just another handsome rake who turned up in guest shots on TV. But his five seasons on 'ER' changed all that. Not only did his role as likable cad Dr. Doug Ross make him a household name, but it also made feature film casting directors reassess him as leading man material.

To put it mildly, Clooney's scored big in that kind of role, and has used his good looks, native intelligence, good humor and smoldering stare to manage a dual career as a serious dramatic actor and a good-time comedic lead. Clooney is unafraid to tackle films that ask serious questions about the world of politics and power. He also knows how to pick vehicles that will sell tons of popcorn.

With the release of the assassination thriller 'The American,' here's betting he does both -- just as he did in varying degrees with these, his 10 best films:

10. From Dusk Till Dawn (1996)
With 'ER' a ratings winner, Clooney caught the eye of Robert Rodriguez, who directed this horror flick written by Quentin Tarantino. Clooney plays Seth Gecko, a lowlife who's on the lam after a bank robbery, and stops off in a strip club that just happens to be full of vampires. (Dontcha hate that?) Since this is a horror flick, the rules dictate that Clooney eradicate as many of them as possible, which he does in graphic, bloody style (a.k.a. the Tarantino Rules). A tongue-in-cheek thriller that helped further solidify Clooney's devil-may-care screen persona.
The American
Based on 36 critics

An assassin (George Clooney) hides out in a picturesque Italian town after an assignment ends badly. Read More

Ocean's 11
Based on 35 critics

A parolee (George Clooney) and his gang plan a big Las Vegas heist. Read More

Confessions of a Dangerous Mind
Based on 33 critics

Television producer Chuck Barris (Sam Rockwell) works as a CIA assassin. Read More

From Dusk Till Dawn
Based on 14 critics

Desperadoes (George Clooney, Quentin Tarantino) and a family encounter vampires. Read More

Good Night, and Good Luck
Based on 41 critics

Newsman Edward R. Murrow (David Strathairn) confronts Sen. Joseph McCarthy's ethics. Read More

The Good German
Based on 34 critics

A U.S. correspondent in late 1940s Berlin helps a former lover search for her missing husband. Read More

Michael Clayton
Based on 36 critics

A "fixer" (George Clooney) at a corporate law firm faces the biggest challenge of his career. Read More

Out of Sight
Based on 30 critics

A federal marshal (Jennifer Lopez) and a robber (George Clooney) fall for each other. Read More

Up in the Air
Based on 36 critics

A corporate downsizing specialist faces an end to life on the road as he nears a travel milestone. Read More

Three Kings
Based on 34 critics

Gulf War soldiers (George Clooney, Mark Wahlberg, Ice Cube) follow a treasure map. Read More

O Brother, Where Art Thou?
Based on 30 critics

Three escaped convicts (George Clooney, John Turturro, Tim Blake Nelson) search for buried treasure. Read More