Sarah Connor Chronicles
Dead Like Me
LOL at Quark. It really was ahead of it's time.
I'd also add the Prisoner to that list of quirky shows that should've stuck around a little longer. That remake of it that came out a couple years ago sucked, despite McKellen and Caviezel's best efforts to keep it on life support through their performances. Show needed a better writers like Steven Moffat or Russel T. Davies.
I'm tempted to say The Wire, because it's such an amazing show and I suspect they could've focused on one, maybe two, more institutions and then quit (I believe Simon planned to do the Church and then the TV media). However, the ending felt clean anyway, so I'm satisfied either way.
He said he only *could* have done one more season and it would have been on Hispanic immigrants but just didn't have the knowledge/insight with them that he had with everything else. Also, imagine how much of the suture and verisimilitude would have disappeared with the wire had there been subtitles or English speakers for Hispanics.