Simple enough. What is your favorite movie for each decade? You can start with whatever decade you like, but I haven't seen many movies from the 20's or before.
1930's King Kong (1933)
1940's The Maltese Falcon (1941)
1950's Godzilla (1954)
1960's The Good, The Bad and the Ugly (1966)
1970's Taxi Driver (1976)
1980's Raging Bull (1980)
1990's Pulp Fiction (1994)
2000's The Dark Knight (2008)
2010's The Avengers (2012)