It has to be the 50's- for reasons outlined by wvq. It was a golden age for Japanese films. From 52-55 Mizoguchi alone directed several masterpieces; Life of Oharu, Ugetsu Monogatari, Sansho the Bailiff, Chikamatsu Monogatari, Tales of the Taira Clan, Yang Kwei Fei. Add Ozu's Tokyo Story, Kurosawa's Seven Samurai, Rashomon, Throne of Blood, Ikiru, Hidden Fortress, and the most admired films by Naruse and Ichikawa.
Not forgetting Sunset Boulevard, All About Eve, Umberto D, Singin in the Rain, The Band Wagon (these 2, in successive years, constitute the peak of musicals), High Noon, The Wages of Fear, Monsieur Hulot's Holiday, Senso, Apu Trilogy, Pyaasa, Paths of Glory, Twelve Angry Men, Bridge on the River Kwai, Some Like it Hot, Hiroshima mon Amour. Bergman (The Seventh Seal, Wild Strawberries) and Fellini (La Strada, Cabiria Nights) hitting their stride, and Ophuls' final period; Le Plaisir, Madame de, Lola Montes.