I compiled this list based on the most recent lists from over 30 different sources, including 24/7 Wall St (IMDB, Rotten Tomatoes), Sight & Sound, Natl Society of Film Critics, Business Insider/Metacritic, Stacker, Filmsite, AFI, Cinema Archives, EW, Time Magazine, Hollywood Reporter, Rolling Stone, Village Voice, Timeout, the Spectator, Roger Ebert, Leonard Maltin, & Halliwell. I came up with a simple point system to assign points to movies based on their ranking on each source's respective listings - no complicated algorithms here. For sites that didn't actually rank them, I allocated points using an avg midpoint value for each film, weighing them equally, and I hope with enough lists, it results in a fairly good measure of the true "GREATS." Probably more skewed towards the critics'/film experts' side rather than what general audiences would choose, but I think it spotlights at the top the movies of greatest influence; e.g., Godfather, Citizen Kane, Psycho, Pulp Fiction, etc.
