I found 10 lists of Best Fantasy Books and compiled them into one meta-list. Here are the results: all the books (or series) on at least three of the original source lists. They are organized by rank, with the books and series on the most lists at the top. Books or series on the same number of lists are organized chronologically. In the case of series, I have included the name of the first published book. In determining chronology, I have used the date of the first book published in the series (note that the first book published is not always the first book in the series because of prequels).
To see a list of the Best Science Fiction Books, go HERE.
On 8 Best Fantasy Books lists
The Lord of the Rings (trilogy, 1954-1956) (first book: The Fellowship of the Ring (1954)). By J.R.R. Tolkien (UK).
On 6 lists
A Song of Ice and Fire (series, 1996 and continuing) (first book: A Game of Thrones (1996)). By George R. R. Martin (US).
On 5 lists
The Dark Tower (series of 8 books, 1982-2012) (first book: The Gunslinger (1982)). By Stephen King (US)
Discworld (series of 41 books, 1983-2015) (first book: The Colour of Magic (1983)). By Terry Pratchett (UK).
Mistborn (series, 2006 and continuing) (first book: Mistborn: The Final Empire (2006)). By Brandon Sanderson (US).
On 4 lists
The Wheel of Time (series of 14 books, 1990-2013) (first book: The Eye of the World (1990)). By Robert Jordan (Brandon Sanderson co-authored final three books) (US).
Harry Potter (series of 7 books, 1997-2007) (first book: Harry Potter and the Philosopher’s Stone (1997)). By J.K. Rowling (UK)
The Kingkiller Chronicle (series, 2007 and continuing) (first book: The Name of the Wind (2007)). By Patrick Rothfuss (US).
On 3 lists
Gormenghast (series of 5 books, 1946-2009) (first book: Titus Groan (1946)). By Mervyn Peake (UK).
The Chronicles of Narnia (series of 7 books, 1950-1956) (first book: The Lion, The Witch and the Wardrobe (1950)) . By C.S. Lewis (UK).
The Once and Future King (1958). By T.H. White (UK).
Earthsea (series of books and stories, 1964-2014) (first novel: A Wizard of Earthsea (1968)). By Ursula K. LeGuin (US).
The Last Unicorn (1968). By Peter S. Beagle (US)
The Chronicles of Amber (series of 10 books, 1970-1991) (first book: Nine Princes in Amber (1970)). By Roger Zelazny (US).
The Chronicles of Thomas Covenant (series of 10 books, 1977-2013) (first book: Lord Foul’s Bane (1977)). By Stephen R. Donaldson (US).
Shannara (series, 1977 and continuing) (first book: The Sword of Shannara (1977)). By Terry Brooks (US).
The Mists of Avalon (first in the Avalon series, 1983). By Marion Zimmer Bradley (US).
The Dark Elf Trilogy (series, 1990-1991) (first book: Homeland (1990)). By R.A. Salvatore (US).
The Sword of Truth (series of 18 books, 1994-2017) (first book: Wizard’s First Rule (1994)). By Terry Goodkind (US).
His Dark Materials (trilogy, 1995-2000) (first book: The Golden Compass (1995)). By Philip Pullman (UK).
Malazan Book of the Fallen (series of 10 books, 1999-2011) (first book: Gardens of the Moon (1999)) . By Steven Erikson (Canada).
The Dresden Files (series, 2000 and continuing) (first book: Storm Front (2000)). By Jim Butcher (US).
Jonathan Strange & Mr. Norrell (2004). By Susanna Clarke (UK).
The Magicians Trilogy (series, 2009-2014) (first book: The Magicians (2009)). By Lev Grossman (US).
The Stormlight Archive (series, 2010 and continuing) (first book: The Way of Kings (2010)). By Brandon Sanderson (US).
The First Law (series, 2006 and continuing) (first book: The Blade Itself (2006)). By Joe Abercrombie (UK).
The City and the City (2009). By China Miéville (UK) (also listed as Science Fiction)