I don't generally read fantasy fiction, despite the fact (or perhaps because?) my partner reads virtually nothing else. However I recently read Francis Spufford's memoir about his childhood reading and he had been a real fantasy fan. This book, Mythago Wood, was mentioned and sounded interesting. Lo and behold it was on my partner's bookshelves! So I read it - its good to read something entirely different to your usual reading once in a while! Mythago Wood is based on an interesting idea about a woodland that exists largely as the result of the collective imagination and is populated by mythagos - people, animals and even buildings that also come from the collective imagination. I found this fascinating, especially the persistance of ancient types in the human subconscious and the subtext that the wildwood is nature waiting to take over all human follies, such as the entire modern world itself. I enjoyed the adventure element of the story too, though it sometimes felt contrived.
In theory I like science fiction and fantasy because of the way they use invented worlds to comment on real life. Escapism with a serious point, if you like. In practice though I tend not to read genre fiction at all.