These are my favorite pre-1960 films, and I will allow you to decide which of them are not fully known:
The Adventures of Robin Hood (1938, U.S., dir. Michael Curtiz)
All Quiet on the Western Front (1930, U.S., dir. Lewis Milestone)
Camille (1937, U.S., dir. George Cukor)
Casablanca (1942, U.S., dir. Michael Curtiz)
Citizen Kane (1941, U.S., dir. Orson Welles)
Duck Soup (1933, U.S., dir. Leo McCarey)
Forbidden Planet (1956, U.S., dir. Fred McLeod Wilcox)
Freaks (1932, U.S., dir. Tod Browning)
The Great Dictator (1940, U.S., dir. Charles Chaplin)
Invaders from Mars (1953, U.S., dir. William Cameron Menzies)
It’s a Wonderful Life (1946, U.S., dir. Frank Capra)
King Kong (1933, U.S., dir. Merian C. Cooper)
La Strada (1954, Italy, dir. Federico Fellini)
M (1931, Germany, dir. Fritz Lang)
The Maltese Falcon (1941, U.S., dir. John Huston)
Modern Times (1936, U.S., dir. Charles Chaplin)
The Searchers (1956, U.S., dir. John Ford)
Seven Samurai (1954, Japan, dir. Akira Kurosawa)
Singin’ in the Rain (1952, U.S., dir. Gene Kelly, Stanley Donen)
The Third Man (1949, U.K., dir. Carol Reed)
The Treasure of the Sierra Madre (1948, U.S., dir. John Huston)
Vertigo (1958, U.S., dir. Alfred Hitchcock)
The Wizard of Oz (1939, U.S., dir. Victor Fleming)