The Biggest Fantasy Series of All Time is...

According to Wikipedia:

J.K. Rowling's Harry Potter (7 volumes, 3 supplements) - 450m
J.R.R. Tolkien's The Lord of the Rings - 150m (Wikipedia classifies it as a single volume)
C.S. Lewis' Chronicles of Narnia (7 volumes) - 120m (The Lion, the Witch and the Wardrobealone - 85m)
Stephanie Meyer's Twilight (4 novels, 1 novella, 1 guide) - 116m
J.R.R. Tolkien's The Hobbit- 100m (Not a series - unless you're Peter Jackson)
Anne Rice's Vampire Chronicles (12 volumes) - 80m
E.L. James' 50 Shades o...