There are many tales from
The Silmarillion that would make a good movie: The Rebellion of the Noldor, Beren and Lúthien, The Children of Húrin (with Túrin), The Fall of Gondolin (with Tuor) (perhaps together with the Ruin of Doriath and the Voyage of Eärendil). These four could make a nice quadrilogy as they're the main ingredients of the Silmarillion proper. The Drowning of Númenor and the Last Alliance would make a good one film, too.
The problem is, that the rights to the Silmarillion are with Christopher Tolkien. Talking him into selling them might prove to be not so easy a feat, mildly speaking.
There's a whole forum working on a Silmarillion movie fan project (
Link) You will even find some resident Downers there.
Here's a site that has a lot ideas on a Númenor movie. (
Link) Made by the same person who runs Ardalambion.
There was a film script for the Children of Húrin somewhere on the net once, too, but I can't find the link right now. I will maybe edit this later.