As I've noted before, I really think this has a lot to do with economics (or perceived economics). Hollywood has this terrible tendency to periodically go into long spates of remakes, sequels, and the like, rather than producing much in the way of original films (or even film adaptations of previously untouched literary material), as it saves money in the initial stages -- proposals, treatments, purchase of rights, etc. They then have either some studio writers or plain hacks take a (slightly) different spin on it, but without any true imagination... and bank on a known title that people can identify with, rather than expending any effort either creatively or financially that they can avoid. (And sometimes they don't even go that far. Cf. Gus van Sant's remake of Psycho.)
In former times, people would get bored and tired of the rehashes, and begin attending more "art" or foreign films, which remained more focused on creativity and originality (or pretentiousness, at times), and Hollywood would slowly wake up to the fact it was losing its audience to these alternatives. And, of course, when that happened, they'd blame the genres themselves ("nobody's interested in sci-fi anymore"; "horror films are passé" -- or "so yesterday", or whatever the current catchword for such a concept may be -- etc.; or even denigrating previously highly lauded filmmakers). (Oh, and I use "skiffy" in this sentence deliberately, to underscore the contempt expressed. As most of those around here know, I utterly despise that term, as it originally -- and, with many even today -- denoted a low-brow, sub-literary form of science fiction-cum-adventure which helped give the genre its negative image in the first place. "Flowers for Algernon", Dune, or The Left Hand of Darkness are not "sci-fi"; Buck Rogers is.)
Eventually, though, they'd get it through their heads that it was their lack of creativity and originality which was costing them the money, and they'd begin financing some of the mavericks who were, until then, having a tough time getting their projects made... or had to settle for extremely watered-down versions of same. Then things would pick up again for a decade or two, until the New Guard became the Old Guard, and the cycle began all over again....
Now, however, Hollywood is so stuck in its "post-modern" idea of what the medium (or art) is, that rehashes and remakes are considered as viable an artistic production as the alternative (original work), and the New Guard is, if anything, even more entrenched in this inspissated manner of thinking; so I'm no longer so sure there's going to be a renaissance... at least, for a good long time. And so, as long as even with the audience, the emphasis remains better technical achievement (visuals, sound, etc.) rather than better storytelling, more originality, more intelligent scripts, etc., then all we can expect are remakes and sequels and rip-offs of rip-offs of rip-offs.
An occasional remake or sequel is fine -- sometimes they even manage to come up with something really good (vide The Fly, Bride of Frankenstein, Aliens) -- but when it becomes the norm... we're in trouble, folks; both as an audience and as creative individuals ourselves, for we reinforce the idea that only "the tried and true" is worth giving a shot, and that is never good for any form of artistic endeavor; literary, cinematic, or otherwise.