is an easy choice (although I must note that I care little for the movie version). For the record, I've never had enough interest to see more than an isolated episode each of any other Whedon show.
And, after tearing through most of the first season on DVD with a blind buy, I have to make a shout out for Alien Nation
. The show offers a more complexly developed alien race than I have seen on any other television series, and despite being a product of the 1980s manages to tackle more adult topics that are still relevant 20 years later than most of what is on television today. A quick google search surprised me in finding that there isn't a lot of information out there about the show. A shame, really. A damned, damned shame.
For one that isn't on your list, I have to mention the Babylon 5 spin-off Crusade
. Yes, it had its missteps, and risked reteading themes of its parent series, but compared to the first 13 hours of Babylon 5 (and also comparing the pilot movies The Gathering and A Call To Arms) it was a far, far superior program at that stage.