I don't watch very many TV shows, but here are my top ten (in no particular order):
1.) Party of Five
2.) Grey's Anatomy
3.) La Femme Nikita (my first serious bf was addicted to this show.

)
4.) ER
5.) CSI: Miami
6.) Buffy the Vampire Slayer
7.) Seinfeld
8.) 60 Minutes
9.) Deadwood
10.) Cheers