It seems hard to believe that there was a time when Star Wars was an unknown quantity whose success was uncertain at best. However, when 20th Century Fox agreed to distribute the film they had to pull some strings to make sure the movie was even seen. One of the theater owners remembers that back in 1977 he wanted to show a film called The Other Side of Midnight, based on a Sidney Sheldon novel, but that Fox basically held him up and told him he could only do that on one condition.
Travis Ried describes himself as being a "rookie buyer" for a theater chain based out of San Francisco in 1977. He told The Hollywood Reporter that he hadn't actually seen Star Wars before he had to decide which theaters to put it in. Of course, once Star Wars expanded into more theaters it became a hit almost instantly. Obviously, more theaters wanted it, but they were then expected to take the other movie, which was likely struggling due to everybody going to see Star Wars.
Apparently, this process of forcing theaters to take a lesser desired movie in order to get the high demand one was not an uncommon practice in the era. Another theater owner says that E.T. the Extra-Terrestrial was pushed on theaters that wanted to screen Poltergeist. The situation was similar to that of Star Wars, as E.T. became the much bigger hit.
Star Wars ' impact on movies can't be understated. In addition to it being one of the first summer blockbuster movies and grossing a ridiculous amount of money it turns out it also changed the business of showing movies. Previously, many theaters had specific deals with studios. One theater would show films from Paramount almost exclusively while another would show movies from Fox. By the time of Star Wars sequel, The Empire Strikes Back all movies were opening everywhere at once, as they do now.
For the record, The Other Side of Midnight did about $18 million in business in its initial release, which was a perfectly respectable number in 1977. Of course, Star Wars went on to become the highest-grossing movie of all time, so, by comparison, it looks like a flop.
Because so much has changed it's unlikely that we'll ever see such a surprise hit the way that Star Wars was. Now, it seems the only question is just how much money will each new movie in the franchise make, and just how long will it last.