Saladin Ahmed writes for NPR about the appeal of Fantasy fiction:
A few years ago, I was fortunate enough to attend an informal lecture/pep talk for up-and-coming fantasy writers by the man Time called "the American Tolkien," the now-world-famous Martin. The grizzled master described the very early days of Tolkien's cult popularity to a room of us wide-eyed newbies. When college students and hippies started hanging up Lord of the Rings posters, Martin pointed out, "It wasn't the book covers or some artist's conception of Frodo that went on our walls. It was the map of Middle-earth."
His argument is that particularly in epic fantasy, it is the world more so than the characters that compel our attention. Certainly exploring fantasy worlds in my reading youth was a huge appeal, and I crafted plenty of unused new worlds with maps and all sorts of elaborate histories (this spilled over effectively into my role playing hobby, where a small group of 'readers' can explore a world without having to worry about complicated things like marketing and publishing contracts and being paid).
Even among writers and readers who agree upon the importance of world-building, there is great disagreement over how to do it right. A thousand blog posts have been launched arguing over how much detail ought to be revealed to the reader. Jordan's Wheel of Time series, in particular, is a sort of perennial target of parody, even among die-hard fans, padded as it can be with relentless descriptions of clothing, hairstyles, furniture and food. And Martin can spend page after exhausting page detailing the coat-of-arms of every attendee at a royal banquet. For readers used to the protocols of literary fiction, novels that come with glossaries and appendices can feel distinctly like homework.
Disclosure: I dislike Jordan's WoT series and enjoy LotR more as an academic text (I have an Arts degree somewhere relating to Medieval/Renaissance Literature) than a fun read.