This Sir Ian McKellan fellow might be a good choice. I hear he has a good eye for direction.
In all seriousness, Guillermo Del Toro is one of my favorite directors, but he is NOT right for the Hobbit. Firstly, it's much lighter in tone than what he usually does(though I'm sure he could adapt to it), he'd have been better for the trilogy itself than the Hobbit. But mostly, Del Toro has a fantastic visual sense. And that's just it, if he made the Hobbit, it would look like a Del Toro film, it would not fit in with the rest of the Peter Jackson trilogy. We'd probably get an amazing film but it would stand out far too much.