I watch ahelluvalot of TV, of the most recent picks there's Lost, Firefly, Rome, Prison Break, Dexter, Deadwood and Jericho.
To start with the great: Rome, Lost, Firefly and Dexter are must-sees and full of awesome. End of story.
I lost my interest in Deadwood somewhere around the the second season, but it's still pretty good cowboy action and you'll never get used to seeing Timothy Olyphant without a mustache and hat ever again.
Jericho had a bunch of uninteresting characters and bad actors to form the moat around the cool setting and interesting plot, which was a damn shame.
Prison Break has simply gone downhill since the first season (which wasn't even that good) and now we're stuck with endless close-ups of the lead character with his never changing 'squinting' look on his face.
I also really like the animated series craze that The Simpsons kinda started.
The awesome: Duckman, Invader Zim, South Park, The Boondocks, Futurama.
Drawn Together was fun for a while, but just got worse and worse until it exploded into outright awful in the third season.
King of the Hill was pretty good, but not really my taste to be honest.
I also watch American Dad and Family Guy but the writing seems to hover somewhere between lame and stupid, so probably not the best picks.
I saved the best for last. British awesomeness follows:
The Young Ones, Bottom, Monty Python, Blackadder and Red Dwarf.
You should all run to your local DVD pusher and buy 'em right now.
(and Spaced is pretty good too, go for it if you liked Shaun of the Dead)