Giant (1956) - Starring Elizabeth Taylor, James Dean and Rock Hudson, this epic set in Texas follows a family from the 1920s to the end of WW2. The film is a staggering three and a half hours long and is one of the only films where James Dean is the lead. Dean, however, was killed in a car crash just prior to the film's release and success.
W.R. Hearst commanded all of his publications to neither condemn nor promote the film as a gesture towards the friendship between the Hearsts and the Welles families. Since Hearst had a near monopoly on U.S. publications in print across the states, it was perceived as a dud film by the public as they couldn't garner a review either way. Remember now, these were times when people relied on papers for their news and pennies were short. Too short to waste on a film with no review from their only news sources.
The film opened to mixed reviews and exclusive theaters anti-Hearst promotions. It still profited. It was only after W.R. Hearst and Howard Hughes' deaths that the film actually gained any notoriety. It's a good film for the history of its back story. Not for it's exclusive artistry.
Bridge Over The River Kwai. The Sound Of Music. The Best Years Of Our Lives. Stalag 17. The Exorcist. Doctor Zhivago. .... There are so many more that deserve to be on this threads list. Sadly, they're not.