There are many indexes of a film's quality, most of them unreliable. Did it win Oscars? Dominate the box office? Garner critical kudos?
Scan the honor roll of Academy Awards and you see how arbitrary the Oscar is as a gauge of a movie's enduring value. Ordinary People, an excellent but not exceptional family drama, prevailed over the boxing classic Raging Bull. Gandhi, a pious biopic, beat out the superior fantasy E.T.: The Extra Terrestrial. Titanic, a supertanker of special-effects, took the prize over that atmospheric panorama of urban corruption L.A. Confidential.
Audit the list of box-office champs and you note that some are evergreens and others merely popular. Of the top-grossing films (adjusted for inflation) of all time, five are certified classics (Gone With the Wind, The Sound of Music, The Exorcist, Star Wars and E.T.) enjoying both critical and box office success, while the other five are spectacles beloved in their day for the novelty or grandiosity of their effects and cinematography (The Ten Commandments, Titanic, Jaws, Dr. Zhivago, and Snow White and the Seven Dwarfs).
To use critical acclaim as a measure of film excellence is futile as using a weather thermometer to take your kid's temperature. As a critic I admit this with great regret, while also noting that even a broken watch is right twice a day: In 1982 the National Society of Film Critics (of which I am a member) voted Tootsie as best picture and Steven Spielberg as best director for E.T. (The New York Film Critics Circle -- of which I was then a member -- went for Gandhi.)
What happens to the quality film that flies beneath the radar? Take this tale of two Christmases: In 1947 Miracle on 34th Street"won multiple Oscars and scored with critics and coffers. The previous year It's a Wonderful Life was neglected by audiences, was dismissed by The New York Times as weak and tanked at the box-office. Today, no one watches Miracle (except maybe to see the young Natalie Wood) and It's a Wonderful Life is a perennial.
No movie is a failure that has friends, to paraphrase the line from Wonderful Life. It became an accidental classic when director Frank Capra neglected to renew the copyright, it fell into the public domain, got broadcast promiscuously on television and posterity smiled upon it. Similarly, the futuristic allegory Blade Runner failed to connect with audiences and critics in 1982 yet resonated with audiences a decade later when Ridley Scott's "director's cut" was released and it was championed as a prescient portrait of multiculti urbanism and machine dreams.