has a movie ever been as good or better then the book it might be based on?

Plenty, though it's a matter of opinion of course.
The Godfather
Jaws
Jurassic Park
Shrek
Kickass (based on comic but same thing applies)

And that's off the top of my head.

A Christmas Carol , Superman The Movie well its based on The Superman Comic Book

To Kill a Mockingbird, I thought both were good

I think it was with the shining. the kubrick version.

The Abyss
Godfather
Jaws

Rosemary's Baby

Winnetou! :-)