Many good got already mentioned.
I watched Fawlty Towers a while ago and loved it. It is a show from John Cleese and his wife.
British humor at its best! Also i love the british english, another good example for this is Downton Abbey.
The original show Upstairs Downstairs is not that good. Very nice english but crappy actors. But if someone
is wondering why Elizabeth McGovern is always looking so annoyingly (Cora Crawley), just look one episode
from the original show and you will get it...
Hm beside all the good running comedy shows i appreciated The IT Crowd a lot. Maybe its because i work in IT...
Standard: Dexter, Breaking Bad, Firefly, Star Trek TNG, Big Bang Theory, Walking Dead, Game of Thrones (But i guess this show is over for me, too many... you know what i mean),
Supernatural (season 8 was the best so far in my opinion after 2 very weak seasons), Buffy, Angel, Friends (back then, now it's boring), Married with Children, Raising Hope, Modern Family,
Stargate Atlantis, I should get a life