I have a lot of favorites. Series that I do regular re-viewings of are: Doctor Who 60's + 70's (Doctors 1-4) with 80's and 2005-2013 less so, Red Dwarf, Batman (1966 series), original series Lost in Space, Sapphire & Steel, original series Tomorrow People, The Hitchhiker's Guide to the Galaxy, the Sky TV Discworld productions, The Wild Wild West, Poirot, Jeeves & Wooster (the 1990 Fry & Laurie series), Wodehouse Playhouse (John Alderton and Pauline Collins), Rocky and His Friends and The Bullwinkle Show, Linus the Lionhearted (another 60's cartoon), Beany & Cecil Show (although I also like the few above mentioned "Time for Beanie" episodes I have seen, original series Twilight Zone, Monty Python, Twin Peaks, The Prisoner, Gerry Anderson's UFO, Randall and Hopkirk Deceased, The Banana Splits, H.R. Pufnstuf, Timeslip, Young Ones, Ace of Wands, Catweazel, and quite a few other US and UK classics. There are also quite a few other classic 60's and 70's cartoon series and a lot of classic 60's through 80's anime I like a lot as well.
I do watch and enjoy modern shows and a lot of documentaries, but without the passionate regular re-viewings. I usually prefer the better written sci-fi and fantasy, as you can probably guess from the above favorites, but it just depends on the quality of writing in each series. I'm currently streaming Wallander with Kenneth Branagh, so there is quite a bit of subject variation. I really enjoy 70's Sesame Street and the original series of The Electric Company along with a lot of 60's, 70's and 80's classic commercials and I really dig old shows with the original commercials in them. In the early 1990's my old friends and I would take acid every weekend and watch a lot of 60's and 70's shows with the commercials, old music videos and that type of stuff, as well as very select groupings of the above mentioned TV series, among others. We all had a real blast re-living our childhoods through adult eyes which never really went away for me.