+1
I hear they're remaking (or reworking, or resomething) Back to the Future already. Or planning to.
Anyway, I don't hate remakes, if only because they don't really change the originals. We still have those, so there's not a lot of harm, save for the few people who might then never see the original. And anyone like that wasn't likely to appreciate it in the first place.
I'll say that the classics that should never be remade are the ones that don't depend on any real effects work, to be sure. Casablanca is probably the universal choice; it certainly can't be done better, and for all the improvements in photography and effects, the film doesn't rely on them at all to begin with, so you can't really improve it. You can only make a very different version of it. I guess that still qualifies, so it depends on how "remade" the remake is.
Ditto for a lot of Hitchcock films, for similar reasons. Ditto for Some Like It Hot. No matter how well-shot and/or crisp a remake is, it can't possibly improve a film that didn't rely on that sort of thing to begin with.
I'll disagree with The Wizard of Oz. I don't particularly want them to remake it, but the potential for an incredibly vibrant visual feast above and beyond the original is certainly there. I don't dig the idea, mind you, but I think you can make a better argument for that one than most classics.