For each Citizen Kane - how many hundreds of idiot movies was made at the same time? Take a look at the movies created in each decade - only a handful are remembered. You remember Charlie Chaplin and Buster Keaton, but what about the scores of other movies from then? They were forgettable, and have been forgotten.

Take a random year - like 1959 when Ben Hur was released and take a look at "notable movies released" - how many of them do have you heard of, or much less seen?

http://en.wikipedia.org/wiki/1959_in_film#Notable_films_released_in_1959

Of the Academy Award nominees for best movie in 1959 I've heard of (and see) two.