I honestly have too many favorite reads and we could be here for hours if I decided to list them all so I'll only list the ones that I have read most recently or have gone back to reread a boatload of times.
Ranger's Apprentice and Brotherband: By John Flanagan. Two of my most favorite series, they are both by the same author and take place in the same world.
The Ascendance Series: By Jennifer A. Nielsen. I believe there to only be four book in this series but it is a very entertaining read full of twists and turns with entertaining characters.
Folk of the air: Holly Black. A three book series that I have read most recently and full of entertainment in the world of the Fae.
Court of Thorns and Roses series: Sarah J. Mas. I have reread this five book series too many times to count and I loved it.
Throne of Glass series: Sarah J. Mas. I also loved this series with many a plot twist and turns and and engaging series.
Crescent City Series: Sarah J. Mas. As well with her other two series this, currently two book, series held my attention all the way through.
Knight of the Realm: Jenifer Anne Davis. This series has three books and was very interesting to read.
Warriors: Erin Hunter. I haven't read this HUGE series in a while although it holds a place in my heart and on my book shelf, but it was enjoyable from start to finish... I believe it has over 60 books and is still growing with a large website dedicated to it and many fans.
Percy Jackson: Rick Riordan. This is a very popular series with a couple spin offs by the author and others.
Wings of Fire: Being another series that I haven't reread in a while, although it is dear to me and a fantastic series over all.