Maybe after he does Battle Angel Alita and possible Avatar sequels.
I personally find him... boring? I don't know, his movies just don't seem to have that much style to them. He lacks a bit in character development, focusing more on special effects.
His movies are so long. And, I kind of see what you mean about being boring, but that's probably because they're so long. I love Titanic though. I just saw that for the first time like 3 days ago, but I still love it.
I think he's kind of more into his own movie ideas than with making books into movies.
Avatar sequels? ...
I haven't seen anything that Guillermo del Toro has directed, yet.
(The Hobbit soon!)
(Wait, is he the guy that directed Pan's Labyrinth? I haven't seen that but I want to) hmm. Well, if he is the guy that directed that, I fear that he would make all the effects look like the ones in that, you know how the creatures look kind of similar, It's the same person who directed Hellboy 2 and the creatures in that look a lot like the ones in Pan's Labyrinth. So I don't really want the trolls and such in AF to look the same as those.
We'll see how he does with The Hobbit.
I still think Peter Jackson would be the best (out of those three) because he is good at epic movies and has experience with the height changing thing and special effects. Plus, I feel like he has committment, like he would want to do the whole series. Also, he seems to like to turn books into movies. (with LOTR and The Lovely Bones)