I don't think it's a trick of the memory or some biological analog to video compression. I think it's just the evolution of technology. "Content", as we like to call it now, is created at a certain technological level with certain expectations about the technology used to play it back.

The Wizard of Oz was recorded on film in the expectation that the film copies would be run through a projector in a theatre. So, when the movie suddenly goes from monochrome to glorious colors, the projectors could be relied upon to keep on passing light through the film the same old way to produce the bright new colors.

TV came along, monochrome for the first couple of decades, and that was where I first saw the movie. I was informed later about the neat color thing, but until I eventually saw it in color on home video, I remembered a black and white movie.

Another technological factor that doesn't get as much attention because it's not as obvious is resolution. Up until this century, TV's had terribly poor resolution, and that too affects your perception and memory of the content. Last year I bought a bluray of the digitally-remastered enhanced and blah blah blah version of Wizard, and I was astounded to see that the Scarecrow's face was really a burlap bag instead of a brownish blob. I could see the fibers and the textures. And in every scene there were new details to explore. It took me hours to watch the film.

I've recently been streaming the old Mission: Impossible tv series. It aired starting in 1966, and so was produced for 525-line color TVs of the time. But luckily it was filmed, so that modern transfers can get full high-def resolution.

The fight scenes are a hoot: You can clearly see that they're stunt doubles. They're not even close. You first think "WTF were they thinking???", but it's not their fault. You'd never have noticed on those old TV sets. Sure the guy flying across the room in a blur with the dark hair is Marin Landau, because we just saw him in a continuity shot about to take one on the chin. But in bluray, it's laughably obvious he's not the one flying through the air.

So it goes. Mostly better.