The one thing about Star Wars was - it was announced in the mid 80's that there were plans for six more movies - one prequel trilogy, and one followup trilogy. THAT much was not a secret for close to twenty years.
Unfortunately, it resulted in six somewhat forgettable films. Unless you're a serious die-hard fan, I bet I can show a clip from either trilogy, and you won't know which one it's from. Whereas, the original three - it won't happen.
What IS unavoidable - is for one, Star Wars is now part of our culture. "The Force", the sound of Darth Vader's breathing, Death Star, Yoda's weird way of speaking - you probably can't go a month watching TV without seeing a reference, however oblique. (For example, on the re-booted Magnum, P.I., Magnum's ringtone for Higgins is the Darth Vader theme.)
The other is, it spawned an extremely strong fanbase. Within months of the original movie, there were paperback stories of Luke and Leia and Darth out there, along with a "canon" and timeline to follow, for consistency. It's hard to change the fact that kids still want Darth and Boba Fett action figures, even though the original movie was 1977, and Boba Fett wasn't even NAMED in "Empire". Ancient history to them. By comparison, it would be like ME playing with toys commemorating Charlie Chaplin. I have a nephew in law who yearly dresses in his Stormtrooper gear (and it's probably more authentic than the ones on the screen, because he's a lawyer, makes way more money than I do, and can easily afford it). I've been on both Disney Star Wars rides (and there's a new one). Fact is, people just love it. I can't begin to count how many TV shows have come about.