The actor is something of a Hollywood renaissance man, having put his well-documented personal problems behind him and established himself in three major franchises - Iron Man, Sherlock Holmes and The Avengers.
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Digital Spy takes a look at five of Robert Downey Jr's best roles:
Less Than Zero (1987)
The first movie in which he was credited as Robert Downey Jr, this Bret Easton Ellis adaptation saw the young actor play a drug addict who steals from his family to fund his habit. Ellis was quite scathing about this movie on its release, but reserved praise for Downey Jr and his co-star James Spader.
Downey Jr donned big eyebrows and a moustache for Richard Attenborough's biopic about legendary screen icon Charlie Chaplin. Critics were wowed by the actor's touching performance, so it was hardly a surprise when he picked up a BAFTA win and an Oscar nomination for his performance.
Kiss Kiss Bang Bang (2005)
After years in the wilderness, Downey Jr hit the comeback trail with a brilliant performance as criminal Harry Lockhart in Kiss Kiss Bang Bang. Val Kilmer provided strong support as private investigator 'Gay' Perry van Shrike, while writer-director Shane Black would later go on to reunite with Downey Jr on the forthcoming Iron Man 3.
David Fincher's absorbing thriller centred on the hunt for the Zodiac killer in the '70s. An obsessive streak (perhaps in tune with the film's director) ran through this movie, as Downey Jr and Jake Gyllenhaal - a crime journo and political cartoonist respectively - go on the hunt for the murderer terrorising San Francisco's Bay Area. Intriguingly, Hulk star Mark Ruffalo also features in Zodiac.
Iron Man (2008)
Downey Jr's comeback was complete when Jon Favreau cast him as billionaire arms manufacturer-turned-superhero Tony Stark in Iron Man. There were wise-cracks and spectacular action sequences aplenty, as Stark's road to redemption in the movie mirrored that of its star.
Should Sherlock Holmes, Tropic Thunder or Wonder Boys have made this list? Leave your comments in the space below.