I think that Peter Jackson did a fairly good job with The Hobbit. The Lord of the Rings were perhaps even better. Still, I don't think that I would be too happy if Peter Jackson decided make a movie of The Silmarillion (if, of course, Christopher Tolkien would give his consent, which is highly unlikely...). I've done some thinking on this matter and from being rather positive I've changed my opinion. To tell the truth, Peter Jackson is one of the last persons I would now like to see as the director of The Silmarillion. The Silmarillion needs a director who can focus on the beauty, the love and the development of the characters amidst all the tragic and fighting. I don't think that Peter Jackson is able to do that. He focus waaay to much on the fighting sequences. I will admit that he has done a great job with the surroundings and would probably do that if he was to do The Silmarillion as well. Unfortunately, doing a great job with the surroundings isn't sufficent.
Part of the problem is The Silmarillion itself. This book (or several books...) isn't written to make a good movie. It's way to long and the dramaturgy isn't quite the one Hollywood is too fond of. The pace is, for the one who isn't familiar with Tolkien's works, perhaps too slow and the entire story too dense. If PJ would make a movie of Silmarillion I think that he would choose a part of it, perhaps the story of Húrin or Beren and Lúthien. The problems I see is that he would focus too much on the fighting, forgetting all beauty and tragic, and also simplifies the entire story (which I even think he did on The Hobbit. It's like he takes for granted that no one has read the story or knows the background so he feels like he need to explain everything. But since it's kind of hard to explain so much in so little time he simplifies it too much and makes the story less good (for the ones who has actually read it) than it could've been).
If The Silmarillion would be a movie I would say it perhaps needed 5 movies? More than one at least. I'm wondering whether Silmarillion would do better as a TV-serie instead of a movie? I haven't seen A Game of Thrones yet, but I'm planning to do that soon. I know that A Song of Ice and Fire is quite different from The Silmarillion but perhaps it would work? The pace could be slower and I think it would be easier to explain things without simplifing them. I will watch A Game of Thrones and see if they succeeded with translating the books to a tv-serie. If not, perhaps I need to reconsider the things I've written above.