My own choice, which I think rather surprised her, is FARMER GILES OF HAM, which I think one of Tolkien's most underrated works: it wd make a great little animated film.
Further thinking has led me to conclude that really, deep down, I'm not so keen on seeing SILMARILLION adaptations after all, and that the project is fraught with far more difficulties than most fans who support the idea realize.
Consider: it's long been observed that the Peter Jackson Tolkien films are at their best when they stick closest to Tolkien, including in dialogue. That's because Tolkien is a great writer, and it's hard to add to a great writer's story and have your additions be at the same level as his or her greatness. Add a subplot to PRIDE AND PREJUDICE, and you run the risk of every word being held up to comparison with Austen's best and, quite likely, be found wanting. And yet there's relatively little dialogue in these tales from THE SILMARILLION, which means almost all the dialogue in such films will have to be created; the scriptwriters will have to provide it, and have it be up to the level of what little Tolkien did include. And if there's one thing we've learned in fifty-odd years of fan-fiction and decades of faux Tolkien generic fantasy trilogies, it's that Tolkien can be imitated but that the imitations fall far, often spectacularly, short. What makes Tolkien 'Tolkien' is impossible to emulate.
And all this is apart from perhaps the most serious challenge: THE LORD OF THE RINGS and THE HOBBIT are relatively 'down to earth', so far as tales of the legendarium go. The 'Great Tales' from THE SILMARILLION are grand, and remote, full of superlatives. The Jackson films are at their weakest when they have to portray, in visual form, transcendent moments (like Galadriel's beautiful and terrible: all shall love me and despair!). It was things like this that led Tolkien to believe that serious fantasy cdn't be adapted for the stage.
Consider the best known of all the SILMARILLION stories, that of Beren and Luthien (or Luthien and Beren, as it might better be called). First, the filmmaker has to cast an actress to play the most beautiful woman who has ever lived. Helen of Troy might have pulled it off, but it's a tall order for a filmmaker (think PRINCESS BRIDE's Buttercup). The film has to include a huge amount of backstory (something both Tolkien and Jackson are extremely good at) in order for this particular tale to make any kind of sense against the backdrop of the larger 'War for the Jewels'. And the scriptwriters wd have to have rights to pillage the whole of Tolkien's middle-earth writings: much of the detail they'd want to use is absent from the SILMARILLION version of the story and is found in the (unfinished) LAY instead.
Beyond this, the filmmaker will have to make what will no doubt be controversial decisions: have Beren and Luthien already consummated their love before ever setting out on their quest? When reading, it's up to the reader to decide how chaste the two were in all those secret meetings in the forest after they "plighted their troth"; but the film will have to chose how it portrays them: as lovers in a romantic (chivalric) or modern (physical) sense.
And all that's why I think, even given the legal restrictions aside (the Estate's not going to license any of Tolkien's material for a long, long time to come), filming the SILMARILLION stories present so many difficulties that we still wdn't be seeing these in the foreseeable future. And that's not necessarily a bad thing.
What I think we'll see next is not an adaptation of a Tolkien story, but a biographical picture about Tolkien himself, a la CSL's SHADOWLAND. The recent British radio piece TOLKIEN IN LOVE covered this ground in documentary fashion; it's easy to see how it cd be recast into narrative 'based on a true story' fiction. Born in an exotic foreign land, orphaned, raised by priests, forbidden romance, lighthearted Oxford days overshadowed by war, the horror of western front, surviving the most deadly battle in history, reunited with the love of his life, and the 'happy ending': THE BOOK OF LOST TALES and the beginning of the Matter of Middle-earth. I wdn't be surprised if they ended it with him writing down that famous line, In a hole in the ground lived a hobbit . . .
current reading: THE TIME MACHINE by H. G. Wells