While I'm at it, if it's finished shows on DVD that you're after, here's my favorites, pretty much in my order of preference:

6- Arrested Development [sitcoms don't make you think, Bruno? you really have to pay attention when you watch this one if you want to get all the phenomenally good jokes and season-old call-backs]
5- Freaks & Geeks [this show is so unbelievably great it pains me to put this so far down the list]
4- Veronica Mars [the third season wasn't great, but the first couple are fantastic - best father-daughter relationship on TV I've ever seen (though sadly you don't see that many)]
3- Buffy/Angel/Firefly [three-way tie]
2- Carnivale [easily the best cinematography of any show I've ever seen on TV (also the best intro) - extremely slow to develop but worth every minute]
1- Avatar: The Last Airbender [the true Avatar - it's a Nick cartoon, but DO NOT let that stop you - try to get at least 6 episodes in]