When Googling for information on epic fantasy (specifically, for a definition), I found an interesting article entitled Quality in Epic Fantasy that provides a thoughtful discussion of the current landscape of fantasy novel production, where many series go wrong, and how to avoid such problems. The author condemns the works of Jordan, Brooks, Goodkind and Eddings, while praising those of Tolkein, Martin, Ursula Le Guin, Sean Stewart, C. S. Lewis and Lloyd Alexander.
I also learned that “epic” fantasy means fantasy on a grand scale (Tolkein, Martin), while “high” fantasy means fantasy with high moral contrast (Tolkein and Lewis, but not Martin). (Everyone else probably knew that already, but it was enlightening for me.)