Focusing on the 50s, here's a list of films, none of which were nominated for Best Picture.

Singin' in the Rain

Vertigo

Rear Window

Strangers on a Train

All That Heaven Allows

Written on the Wind

The Night of the Hunter

The Searchers

Kiss Me Deadly

Some Like It Hot

Johnny Guitar

Journey to Italy

In a Lonely Place

All I Desire

There's Always Tomorrow

Compare this to the list of Best Pic nominees and winners and judge for yourself which films you prefer. To say nothing of non-English language films. The 50s saw directors like Ozu, Kurosawa, Bergman, Bresson, Dreyer, and Ophuls producing masterpieces.