I’m in agreement for Hugh Laurie and Stephen Fry.
Neil Gaiman is an excellent narrator (he does a lot of his own books).
Also, Tim Curry is an amazing audio book narrator…very dry, and underplayed (as opposed to overplayed). (He’s done the Sabriel books and A Series of Unfortunate Events.)
I’m in agreement with @Darwin: Jim Dale is excellent at narrating. He was great reading the HP series, and great on Pushing Daisies.
Billy Crystal for Calcifer, Mike Wazowski and Miracle Max.
John Hurt for “The Dragon” on Merlin.
Also, I don’t know if he does audiobooks, but if he did, I would listen to Anthony Stewart Head all day long (in his Giles accent, not his native one).
And, of course, Alan Rickman.