This sort of thing is hard to answer. I still love King Kong (1933) , revere it, and talk about it. But King Kong was still showing as a leading feature in movie theaters around the time I was born (true! – RKO continued to milk that cash cow for all it was worth with lots of re-releases). By the time I was a young kid, it was released to TV and was shown over and over again, because it gave the broadcasters the most bang for their syndication buck. I kept up with it, and it stayed current with me and my friends because magazines like Famous Monster of Filmland featured it prominentkly. Gold Key/Whitman released a comic book version about 1968, and the Delos W. Lovelace novelization from back in the 30s was released in paperback. Then it had the good fortune to have its “censored” scenes re-discovered, and they were re-installed to great fanfare, with a cover article in Esquire and yet another theatrical re-release. Then with the advent of VHS and laserdisk, it got another boost. It got another when it was re-released at long last in the US on DVD coincident with the release of the remake (although not as big a boost).
So King Kong was an interesting and iconic movie not only because of its technical innovations (which were many – KK would deserve a place in film history even if people hated it) and popularity at the time, but because people were actively keeping it alive – it still managed to turn a profit. RKO and its sccessors reaped rewards from theatrical re-releases, television syndication, all forms of video sales, and from licensing of products like those comic books.
Will King Kong continue to draw interest in one or two generations, when this sort of life-support is gone, and those influenced by it are as well? Maybe. The “life support” may continue, if the product continues to sell. If the appeal of the film continues – in spite of or even because of the now quaint pre-CGI effects, as in the case of a classic book, then then people will continue to watch and discuss it. I think we’re still too close to the time it was made, still experiencing the far ripples of the publicity, to tell yet.
Classic books are still read and loved, long after they’re out of date. You can still read Mark Twain’s books, or Jules Verne’s outdated science fiction, or H.G. wells’. A greatv many more books of science fiction have virtually disappeared, even though they were extremely good and, I would have thought, worthy of retention. Whether something IS recalled and treasured is subject to all sorts of factors. Godzilla, I think, got a toehold in the US market because it was cheap, so it could be shown again and again.
There are films that do seem to have acquired a special place – Casablanca, King Kong, It’s a Wonderful Life. Whether or not they will stay there, I don’t know. I suspect that the first Star Wars film, at least, will keep such a special place as well, and will continue to long after it appears very quaint. Time will tell.