Can't believe I omitted replying to this question - but 2 series I absolutely love and one I reread at least once a year - THE LORD OF THE RINGS TRILOGY. I'll admit to skipping through one or two chapters, especially in Book One, but the story just grips you.
After that my all time second favourite is the HARRY POTTER Series. I had the joy of anticipation, waiting patiently each year or years for the next release. The next generation will never have that thrill, but it will be a series read for generations.