Sherlock is no The Wire, but Mr. Robot makes it look like that sometimes.
(Caveat: I'm now only 2 eps in, but OTOH: consensus seems to be that Mr. Robot gets worse, not better).
Adequate, sure! Best TV series ever? Strange.
I was forced to watch Buffy, but while the first season makes you cringe, it is pretty good. Not as stellar as people claim, but really good. I think Joss Whedans masterpiece wasn't Buffy, it was Toy Story. But do watch the musical episode "Once More, With Feeling"!
Babylon 5, of course, if you can tolerate the (even for the time) bad CGI.
I've just watched DS9 from beginning to end, something I had wanted to do for 15 years now. Hasn't aged well, and I hadn't seen it in English before. Avery Brooks' overpronunciation is painful, but it is the best Star Trek series by far.
Friends was something I've enjoyed as a teen, and later as an adult. It was a totally different experience as an adult. I think that's worth a lot, to have a depth that appeals differently to you in different stages of your life.
Modern Family was way better than expected.
ALF is a bit painful to watch nowadays, it also hasn't aged well.
Golden Girls are probably still great, The Cosby Show definitely is!
Boston Legal is fun, fun, fun! Hey, why shouldn't Nantucket be allowed to habe its own nuclear weapons? But do watch all the newer Star Trek series before BL, so you can appreciate the ST heavy cast.
Dallas! Oh my. Incredible how old Victoria Principal is today.
ER was great, but I haven't seen much of the last seasons. I also liked Chicago Hope, but it clearly lost.
The 2004 Battlestar Galactica. Probably the most modern TV series of its time, great themes and issues, pretty current, fantastic buildup to the big finale and then... disappointment.
Game of Thrones, if only for the shock value ;-)
And at last, the Tv series I've probably enjoyed most in the last few years: the first two seasons of Veronica Mars. But make sure you can stomach it, the season finales are sickeningly evil (especially season 2).
My top recommendations would be Twin Peaks, My So-Called Life, Freaks and Geeks, Sports Night, and Arrested Development. I like a lot of shows that get cancelled "early".
The "myth arc" episodes of the X-Files are worth it, but don't try to sit through all 9 seasons. Recently, Better Call Saul is awesome for the emotional depth and film noir aspects, and the previous Breaking Bad to which it's a prequel is still a masterpiece even though I find the premise implausible. The Walking Dead is seriously addictive too.
I got sucked into Elementary a bit (Lucy Liu is very good, didn't expect that), but decided after half a season, it's not that great to justify the investment of time.