NK Jemisin is one of those authors who, no matter how good I remember her being, is better than that. Her work is gorgeous and gut wrenching and she is one of the best Epic fantasy writers I have ever read. Her characters are more real than most people and the world she constructs in the background of their stories teems with life in its own right.
Basically, any list of the greatest Epic fantasy that does not include at least one of her works is woefully incomplete.