This one, to me, is a three-show race. Barney Miller, Benny Hill and Breaking Bad.
Breaking Bad was just so solid and so smart from episode 1 all the way to the finale, it is hard to vote against it. And that train heist episode was one of the greatest episodes of any show ever.
I'm one of the few people in the world who didn't like Breaking Bad. At first it was cool, but much like Weeds - it just got too ridiculous for my tastes.
While Breaking Bad is one of the best shows ever, the fact that Buffy didn't make this final list (while it is a list of very good shows) is disappointing. It was clever, witty, dramatic and had some of the most original scripts ever (Hush and whatever the musical show was called). I never watched Buffy when it was being aired by the networks because, like most viewers (probably), it seemed like a really idiotic premise. After a GF got me to watch it however, I was struck by Joss Whedan's genius. It was a really great show.