There a number of series (some mentioned) that I really enjoyed, but at some point stopped enjoying to read over again so I only included those I still come back to. (Also I would recommend not limiting yourself to JUST series as you are missing out on most of the best books)
- The Kingkiller Chronicle by Patrick Rothfuss (at least so far, there’s still only 2 books).
- The Asian Saga books by James Clavell.
- The Dune Series by Frank Herbert.
- Isaac Asimov’s Robot series.
- Gene Wolfe’s 2 Wizard Knight books.
- Mary Doria Russell’s The Sparrow and Children of God.
- Any of the Ender series books by Orson Scott Card (except Ender’s Game)
- The Harry Potter series by J.K. Rowling.