To determine which films are "classics," PrettyFamous considered movies that were released in or before 1975. The remaining movies were then ranked according to their Smart Rating. This is a score out of 100 that takes into account a movie's Rotten Tomatoes' Tomatometer and Audience Score, IMDb rating and votes, Metacritic Metascore and Gracenote rating. Only films with more than 25,000 IMDb votes were eligible for the list. In the case of a tie, the movie with more IMDb votes was favored.
It's important to note that PrettyFamous' Smart Rating typically weighs a movie's U.S. inflation-adjusted box office gross, but the box office data from the beginning of the 20th century is flawed or lacking. PrettyFamous thus decided to modify the Smart Rating to exclude box office numbers, thereby making the Smart Rating more consistent among all classic films.
Here are the top 20.