I'll go for Guillermo del Toro personnally. He knows how to adapt a story to the big screen yet staying true to its spirit, he has a great sci-fi fantasy universe and I love how he deals with special effects. With him the fairy world would look amazing, and the wittiness and the emotion of the story will be just like, if not better as in the books.
My second choice would be Jean-Pierre Jeunet. I simply love his style and humor, and I pretty well imagine Haven City looking like the City of Lost Children. But I'm not sure I can picture Ron Perlman as Butler or Dominique Pinon as Root or Cudgeon though x)
I'm not a huge fan of the idea of Peter Jackson or James Cameron. They are good directors, but their style is a bit too ''epic'' and SFX-based for the first books in my opinion.