I'm not even sure God Emperor would make a good movie,there's some decent action but mostly off screen (well very short in the book I mean but most action is in Dune) and so much is Leeto just talking to Monro. Though it is my favorite of the series, I'd be curious how they portray Leeto.
As for the rest, I enjoyed them and listened to multiple times but more to hear the lore I may have missed than enjoying the entire story. I did like Teg and more Duncan and the Bene Gesserit more, but I didn't care for the Honored Matres and other factions too much.
To be fair to the Dune universe, the reason they used swords was because shields made projectile weapons useless and Lasguns and shields just killed everyone (like a mini-nuke on both sides).
God Emperor would make a weird movie, but could probably work as a limited series. In my opinion, the two last books are the ones best suited for adaptation. Especially Heretics has a perfect balance between intrigue, drama, action and sex.