But the "trilogy" has seven books (not counting several others written by other writers). And if you include the robot stories, and Baley/Olivaw detectives, Robots of Dawn / Robots and Empire, and the Galactic Empire series, there are 18 books written by Asimov that can be read more or less chronologically. Although some of those aren't that good.
Yea, I started the same way with the original Foundation trilogy before getting ALL the other books eventually...takes up a whole shelf all by itself.
As far as Dune goes, my wife had it pretty much nailed in considering the movie/miniseries versions:
David Lynch got the 'look' right, but fairly tore up the story.
The SciFi channel got the look wrong, but stuck a lot closer to the story. She enjoyed the 'Children of Dune' mini-series more so than the 'Dune' miniseries (oh look at the funny hats).
FastCargo