7. The Princess Bride
Heres an example of a movie that opened with little fanfare but has become part of our collective pop culture in the years since. It practically defines the term cross-genre appeal. It has romance, comedy, drama, action, some elements of fantasy and above all a great sense of adventure. Its also endlessly quotable and stands up to repeated viewings. This is the kind of movie that can easily be passed down from generation to generation, much like the book that the grandfather reads to his grandson. At this point, refusing to acknowledge its greatness by not adding it to the registry would be inconceivable.