I haven't watched much broadcast television since I started graduate school. In the first few years in Pittsburgh we didn't have a TV in the house and I fell out of the habit. About ten years ago my wife and I started buying or borrowing DVDs and working through particular shows that I'd heard were good. The first was Mad About You, followed by Buffy The Vampire Slayer, 24 (season 1 only; my wife found the cliffhanger endings intolerable), Fawlty Towers, Band Of Brothers, Angel, new Doctor Who, new Battlestar Galactica, The Wire, and a couple of Hong Kong kung-fu shows that I can't explain. We started a few other shows and then abandoned them after discovering that my wife or I didn't like them.
Most of those shows are very good. The Wire is exceptional. Lots of other people have written about it more eloquently than I can. I can understand why the mayor of Reykjavik semi-seriously demanded his allies watch all five seasons. Anyone interested in politics or social institutions should watch it.
However, the best of the lot is Buffy The Vampire Slayer. It starts as silly fun --- and remains so --- but as it progresses, it constantly reveals new levels of creative genius. The imagination, writing, execution are staggering. It's not flawless, but it's the only show I seriously consider watching again. It's not for everyone, but it is undoubtedly great art.