[Elladan and Elrohir]

Well, obviously, it's impossible to try to adapt the whole thing. Literally impossible. The result would be horrific if anyone were stupid enough to try.

I'm an aspiring filmmaker and it's my dream to one day be able to make Silmarillion-based films. Of course, I fully realize the odds of that happening. Even if someone in a position to make the movies wanted badly enough to do them, you'd have to purchase the film rights from the Tolkien Estate. I doubt that's even possible while Christopher Tolkien lives.

In my dream world, my Sil films would be:
(1) Beren and Luthien
(2) The Children of Hurin
(3) The Fall of Gondolin
(4) The Downfall of Numenor
(5) The War of the Last Alliance

(1) would make a spectacular movie, IMHO. Has all the ingredients. But a huge undertaking. (2) would be spectacular as well; the only downside is that the ending is gut-wrenchingly sorrowful. I'm not sure audiences would put up with it. (3) would be more like a Star Wars Episode III deal where yeah, Gondolin falls and Turgon dies and Maeglin betrays everybody, but you do have "A New Hope" in the form of Earendil. (4) and (5) would ideally be filmed back-to-back, or at least with your Elendil/Isildur/Anarion actors returning, with (5) concluding with the Disaster of the Gladden Fields.

However it would be done, it would be a massive undertaking. It really does dwarf LOTR because with LOTR, you have a 1000-page novel plus appendices to work with for your story. With these, there certainly is a variety of material from Silm, UT, HoME, and the forthcoming CoH, but you have to do a ton of extrapolation. It's going to take a director with a strong commitment to Tolkien, a vision to truly bring the stories to life, and an imagination the size of Mount Everest. Depending on the director, these stories could be crafted into some of the greatest films of all time, or they could be big fat duds.