Surely many of us are also fantasy readers (an assumption, sure, but I bet it is a fairly good one).

What author presents the best maps in his books?

Who does the best job of world building, creating a vibrant, interesting, and fully realized world?

As to maps, most maps in books need to be simple due to limitations on the size and (often) black and white nature of book maps. I always liked David Eddings maps, simple, but often with a more detailed snippet at the start of a chapter. Raymond Feist books present clean and effective maps, as do Robert Jordan's and George RR Martin. I could go on, but maybe later...

As for actual world building, I have to give the hat tip to Robert Jordan. Love him or hate him, he has clearly created a world with well defined cultures, politics, demographics, etc. I suppose have a dozen 700 page books to work with does not hurt!