E.T. stayed relevant for a long time due to Spielberg's shrewd marketing strategy: he refused to release it on home video.
He had a re-release in 1985, but still no VHS tape.
All you really need to do to convince people that they NEED something is to tell them they can't have it. For a few years, E.T. had an almost mythical status cause there was no way to watch it at home.
SIX YEARS after the movie was out, he finally announced a VHS release date. October 1988. People lost their minds. Couldn't wait to watch it over and over, share with the family, etc. VHS tape broke all known sales records.
But once people owned the movie, the mystique was gone. They watched it once or twice, realized it wasn't as good as they remembered, and it became just another hit movie of the past that people like, but very few people love.
Not releasing it was the smartest thing he did. But he wanted one more sweet payday, so he gave everyone what they wanted, but it kind of killed the legacy of the movie.
I don't think that's even possible today. EVERYTHING gets out, either legally or illegally. I remember being blown away as a child in 1986, seeing Captain Eo in 3D on a big screen at Epcot. I remembered it for years..had this feeling it was this amazing timeless thing.
Now you can watch the whole thing on youtube. It's really stupid. It's Michael Jackson and some muppets.
Studios need to start holding stuff back again. Make movies a big deal again. Don't stream them a week after the world premiere. They're such dummies.