A meeting with Lazarus Long was inevitable...
The first SF series I every bought was E.E. 'Doc' Smith's Family D'Alembert sequence. Some kindly relative bought me Volume 3, The Clockwork Traitor for Christmas 1977 or thereabouts. I was hooked on the background and the adventures of Jules and Yvette and the Circus of the Galaxy. (Note; It seems that most of the work on the series was done by Stephen Goldin. An original version of The Imperial Stars appears in The Best of E.E. 'Doc' Smith without Goldin's by line.)
Next came more 'Doc' Smith. The Lensmen series. By today's standards the writing is simplistic, but the rip-roaring adventures of Kimball Kinnison and co were just what a boy in his early teens needed. I had a tear in my eye as I read the concluding pages of The Children of the Lens.
Larry Niven came next. His collection Neutron Star lead me to Known Space, Beowulf Shaeffer, Gil 'The Arm' Hamilton, Louis Wu, and the Kzinti. I found The Mote in God's Eye which lead me to Jerry Pournelle and the CoDominium and John Christian Falkenberg.
Somewhere amongst all of this came C.J.Cherryh's Alliance/Union universe, starting with Downbelow Station, then Cyteen and the books that followed.
Robert A. Heinlein's juvenilles had grabbed me with Tunnel in the Sky. When I found the collection The Past Through Tomorrow there was reference to his Future History and I was off and running. A meeting with Lazarus Long was inevitable...
More recently there has been David Webber's Honor Harrington, along with William Gibson's Sprawl series (Neuromancer, Count Zero, Mona Lisa Overdrive). David Feintuch's Hope series is there too.
Oh, yeah. There's also the original Foundation trilogy and the original Dune trilogy.
My most current series is by Walter Jon Williams, called Dread Empire's Fall. So far all I've read is The Praxis. Looking good so far.
Well there's a selection, from Space Opera to Cyberpunk to right wing military SF. Enjoy.