I agree the 20s and 70s were excellent decades for movies. But my favorite decades are surprisingly the 2000s and 2010s (the 2020s suck so far though), which had an absolute explosion in independent cinema spitting out unique auteurs around the globe.
For the 70s, some of my favorite movies include:
Bernardo Bertolucci's The Conformist (1970)
Bernardo Bertolucci's Last Tango in Paris (1972)
Werner Herzog's Aguirre: The Wrath of God
Nicolas Roeg's Don't Look Now
Francis Ford Coppola's Apocalypse Now
Stanley Kubrick's Barry Lyndon
Jean Eustache's The Mother and the Whore
Brian de Palma's Carrie
Michelangelo Antonioni's Zabriskie Point
Honorable mentions: The Texas Chainsaw Massacre, The Passenger, Salo: 120 days of Sodom, Fellini's Roma, One Flew over the Cuckoo's Nest, The Ascent, The Conversation, The Discreet Charm of the Bourgeoisie, Solaris, The Mirror, Stalker, In the Realm of Senses, American Graffiti, Cries and Whispers, Nashville, Chinatown, The Godfather pt 1+2
