My favorite series, which happens to be written by my favorite author
(Terry Brooks) is definately the Shannara series.
The First Trilogy
The Sword of Shannara
The Elfstones of Shannara
The Wishsong of Shannara
Followed by another series
The Scions of Shannara
The Druid of Shannara
The Elf Queen of Shannara
The Talismans of Shannara
Then Terry Brooks wrote the Prequel to the entire series
The First King of Shannara
And apparently he's written a whole new trilogy based on Jerle Shannara
(who many of the main characters in the novels descended from)...
In my opinion... probably the most addictive series available, even today.
http://isleofavalon.com/walker/shannara/the_books.html 
