Moonwalker has value, but I don't know if I'd call it any kind of classic.
I would say Speed. When I saw the ads, I thought it would be trash, and reading about it later on, everyone involved thought it would be trash, even the actors. Then it was released, and ended up the biggest movie of the summer.
Moonwalker is a classic because Michael Jackson INVENTED the long form music video in its current incarnation with Moonwalker. Nothing like it ever existed before and it paced the way for all the story driven music films after it.
Smooth Criminal by itself is a classic.