I'm mainly judging a book by the prose and themes that are explored, and it JUST SO happens that most fantasy is poorly written and are otherwise quite shallow.
Gene Wolfe is just a master at the craft which is why Book of the New Sun is so good, and Bakker explores an interesting and compelling world while incorporating a deep philosophical aspect into his books.
The greeks are a must for anyone who ever wants to read anything and Tolkien is thee classic.
What else is there is just filler at the end of the day.