To clear things up, I am not comparing the the original trilogy to the prequel trilogy, nor am I comparing the original trilogy to the animated Clone Wars series. I am actually comparing the trilogy to films in general.
Whether or not you are a fan of science fiction, you have doubtlessly heard of this fantastic franchise, from the black-clad Darth Vader to Yoda's signature words of wisdom : "Do or not, there is no try." Whether you have seen it and loved it, seen it and disliked it, or you just haven't gotten around to seeing it yet, this classic trilogy was insanely popular and successful.
This is why...
Star Wars Was Supposed To Fail...
During production, few people had real faith in the first installment in the franchise: A New Hope. George Lucas felt like the movie would be an utter failure, and when he showed an early version of the film to some of his director buddies, Brian De Palma (director of Scarface and Mission: Impossible) called it the worst movie of all time. Harsh words, but they were agreed upon by many industry. The only person to show real faith in A New Hope was Steven Spielberg, who predicted that the film would generate millions of dollars.
During the premiere of A New Hope, George Lucas was so sure that it was going to crash and burn that instead of attending the premiere, he went on a vacation with Spielberg to Hawaii (where, oddly enough, they brainstormed the idea for Raiders of the Lost Ark).
...But It Didn't
The original Star Wars film was very-well received, which stunned Lucas. Even the film's music, written by John Williams, is now number one on AFI's 100 Years of Film Scores. Just during the opening weekend, the film raised over 1.5 millions dollars. If the sales were adjusted for inflation, A New Hope would be the second-highest grossing movie in the history of film! Even if it wasn't adjusted, it would still be in the top-50 grossing movies!
20th Century Fox was initially close to selling their stake of the movie as they saw it had low promise. Luckily for them, they stuck with the film, and the profits of Star Wars prevented the company from bankruptcy. The success of this movie prompted Lucas to turn this stand-alone film into a trilogy that we know today.
Star Wars Launched the Movie-Toy Industry
George Lucas pulled a major risk when it came to merchandising. He wanted full-merchandising rights, so he made a deal, accepting a lower salary in exchange for the rights. Many saw this as a foolish deal, as movie-based toys had never made much money. However, when the holidays came about in 1977, sales exploded for Star Wars toys and movie merchandising has never been the same since.
Other Science Fiction Franchises Look To Star Wars For Inspiration
Seeing as A New Hope was the first science fiction film to be nominated for an Academy Award for Best Picture, many other films and television series looked to the Star Wars films as a reference.
Joss Whedon's Firefly series was based heavily on the franchise. In one of the shots of the pilot episode, you can see an Imperial shuttle flying by. They also cleverly hid miniatures of Han Solo frozen in carbonite in every episode.
Other similarities can be found in franchises like Star Trek and Battlestar Galactica.