Most great science fiction movies are from books and short stories written by Phillip K. Dick
I'm still waiting for the film treatment of "Counter Clock World"
Ubik would be good as well. So would The Three Stigmata of Palmer Eldritch.
But they are a bit obscure and would probably make Dune seem like The Cat in The Hat by comparison.
Phillip Kendall Dick was the greatest science fiction writer ever.
If you haven't read Valis, get it. Very autobiographical.
You are so right.