Robert Downey Jr. Turns 51: 6 Non Marvel Movies to Celebrate Iron Man's Birthday!

Though these days he's known for being the highest-paid actor in the world and the megastar of one of Disney's biggest franchises, the Marvel Cinematic Universe, Robert Downey Jr. has been proving his worth as an actor for over three decades now. It's the Oscar nominee's birthday, so let's review 6 of his most notorious movies -- even beyond his time as Iron Man!

1. Chaplin (1992)

In the biopic directed by Richard Attenborough, Downey plays film legend Charles Chaplin on the road that led to becoming a star all the way to his years of exile, and Downey's spectacular in the role. He pulled off the English accent, performed his own stunts (15 years before Iron Man) and showed a vast performance range. This is arguably Downey's best work.

2. Natural Born Killers (1994)

In this Oliver Stone-directed film from a Quentin Tarantino story, Downey plays a drug-addicted Australian tabloid journalist who documents a serial killing couple. Filmed during Downey's actual time as a struggling addict, it wouldn't be surprising to hear that he took some of his own experience for the role; whatever the case, he nails it.

3. Only You (1994)

For this romantic comedy from the mid-90s, Downey teamed up with Marisa Tomei. Endlessly cute date movie material, the two stars have a lot of chemistry together and it's positively refreshing to see Downey tackling such a lighthearted role.

Rumor has it Tomei will be playing Aunt May on this year's Captain America: Civil War, so they might share the screen for the first time in two decades!

4. Kiss Kiss Bang Bang (2005)

A few years before embodying billionaire superhero Tony Stark, Downey played arguably his un-coolest character ever, Harry Lockhart. In the quick-witted film, Downey plays a thief flown into Hollywood to play a detective, and he teams up with Val Kilmer for research until things get complicated.

This movie is really something of a gem. Besides, how often are Batman and Iron Man together in the same film?

5. A Scanner Darkly (2006)

There are plenty of reasons to watch the Richard Linklater-directed animated adaptation to Philip K. Dick's story, and Downey's definitely one of them. Playing part of a crew of drug addicts (in a film starring the likes of Keanu Reeves, Winona Ryder and Woody Harrelson), the actor has some of his best -- and quirkiest -- moments on film here.

6. Tropic Thunder (2008)

This film came out the same year as the first Iron Man installment, and it marked part of Downey's big return to the screen. He's hilarious in the role of a Method actor who takes it too far, and he got his second Oscar nod for his performance here.

There are plenty of other great Downey performances, from the film that made him a star, Less Than Zero, to his Sherlock Holmes and last year's The Judge. In all, try to catch any movie starring Downey today and every other day. Happy birthday, Mr. Stark!