The Guardian are running a poll to vote for the top show of this decade, the list is pretty decent with many worthy mentions on it:

24
30 Rock
Arrested Development
Band of Brothers
Battlestar Galactica
Big Brother
Black Books
Buffy the Vampire Slayer
Curb Your Enthusiasm
Deadwood
Dexter
Doctor Who
Extras
Family Guy
Firefly
Flight of the Conchords
House
Jam
Life on Mars
Lost
Mad Men
Oz
Peep Show
Planet Earth
QI
Rome
Shameless
Six Feet Under
South Park
Spaced
Spooks
State of Play
The Daily Show with Jon Stewart
The Office
The Shield
The Sopranos
The Thick of It
The West Wing
The Wire
Top Gear

This being The Guardian, the smart money is on The Wire winning, but most of these shows deserve to be on the list (except for Spooks imo).

You can vote for your favourite at http://www.guardian.co.uk/media/poll/2009/jul/28/best-tv-show-noughties

Edit: At this stage the votes are being heavily weighted by Top Gear and QI fans, which has turned the entire thing into a quite brilliant and whimsical farce. But that's what happens when technologically adept fan(atic)s band together and also create 'sock puppet' votes to inflate their favourite show's standing.

In short, the Guardian really didn't think this one through and as such it's become a two horse race between QI and Top Gear, two excellent shows but neither one really deserves the title as 'the best' compared to many of the other shows there. And that's just hilarious.