Here's a list and why.
1. The Wire - This is the best show ever made for television. Nothing comes close in terms of sheer scale and brilliance in authenticity. Everyone may assume it's "just a cop show" but it's anything but that.
2. Batman TAS - Without a doubt the best animated series ever made in America. Cast by professional actors and written by fans the series was the best take on the character that ever see the screen. It was so good it won Emmy's for it's writing, played in Primetime and changed the comic itself
3. Cowboy Bebop - Any best anime list will put this series at the top or near it. Iconic characters, a great plot, a briliant mix of western cinema with eastern culture and the best television series soundtrack ever made thanks to Yoko Kanno. It's the only anime I've seen that hooks people regardless if they love or hate anime. Required viewing for anyone into Anime
4. Six Feet Under - A brilliantly written, raw and dark drama surrounding a family by Alan Ball (writer of American Beauty.) This series was well acted, deep and unflinching, while at the same time holding plenty of black humor along the way.
5. The Shield - The most intense cop show ever made, this one took a look at corruption in LA's gang unit (based loosely on Rampart Division CRASH Unit of LAPD). This show pulled no punches and takes a hard look at gang activity in LA while creating a cast of distinct characters all played so well they could be real people. It fits as almost a west coast answer to The Wire.
6. The X-Files - Nuh Said. Easily the best show of the 1990's, while the series fell apart in later seasons the first five are gold.
7. Firefly - Best series created by Joss Whedon, this short lived sci-fi series felt real without all the usual tropes of scifi galaxy spanning directions most shows about spacetravel take. This one had a small cast on the crew of a boat doing what they can to make a living. It's Whedon at his best.
8. Supernatural - This show may sound typical (brothers go hunting monsters) but it is not. Having one of the best written plots ever on network television this well acted intense series was created by a man who understood good literature and how to create a hero. With references to Joseph Cambell, Neil Giaman and Hellblazer, it's an amazing series. It takes risks that few shows are willing to and was called by one of the creators jokingly as "the most nihilistic show on television"
9. The Prisoner - An old series from BBC. It was the last concept show that didn't focus on a plot or characters, but rather one thing. A man wakes up in The Village and must get free from whomever is holding him. This brilliant unraveling of the 1970's spy genre is almost 1984 the series with some incredible scenes and nearly won a Hugo for it's final episode. "I am not a number, I am a free man."
10. South Park - Name one comedy series that is still consistently relevant and hilarious after 13+ seasons on the air or had more of a presence.
Best shows on currently:
Breaking Bad - The lead actor is incredible. This series is not a mere Weeds clone. For all the black humor it takes itself seriuously and ever actor lets it show through.
Daily Show/Colbert Report - Still always good for hearing hilarious stuff about current affairs and hearing some good interviews.
Burn Notice - While it's forum driven the series is well acted, clever and hilarious. Unlike other shows that have taken a swipe the Spy Genre this one holds to the realism of using people, waiting around and gathering information rather than focusing on a glamorous fantasy. Not to mention Bruce Cambell as a boozing, ladies man always worth the watch.
House - I'm sure most people with AS love the character. He's a total jackass, but I will continue to watch to just hear everything House has to say.
Californication - Almost the successor of Six Feet Under, this show is the funniest and best drama on TV right now. Clever, satirical, and completely heart wrenching at times. I'm still eagerly awaiting season 4.