Here is my personal list, in order of preference -
1. Blackadder
2. Fawlty Towers
3. Seinfeld
4. Peep Show
5. Arrested Development
6. Porridge
7. Knowing Me, Knowing You/I'm Alan Partridge
8. Rising Damp
9. Curb Your Enthusiasm
10. 15 Storeys High
11. Red Dwarf
12. Green Wing
13. Only Fools and Horses (grandad years)
14. Black Books
15. The Larry Sanders Show
16. The Office (UK)
17. Cheers
18. The Mighty Boosh
19. Spaced
20. Father Ted
Moving this to General Discussion, as it'll undoubtedly include a hefty chunk of American programming.
20 is hardly a challenge!
Pretty much the same as your list except:
Take out all the American ones (either rubbish or I haven't seen them - Cheers is good but not top 20) and 15 Storeys High because I only know the radio version.
Replace with Dad's Army, Father Ted, Reggie Perrin, Yes Minister/Prime Minister, Steptoe & Son and Drop the Dead Donkey.
Reshuffle to put them in the right order.
I'm going to do mine two at a time and in no particular order cause I'm tired and will soon need an afternoon nap.
1) Office: An American Workplace
2) Blackadder
I'd like to see a thread where we rank every single sitcom we've ever seen over our lifetimes in order of quality.
Somebody else start, I'll join later. 
Yeah, but I'd only go and knacker it by including some that I've made up, which nobody ever seems to notice!
Quote: john lucas 101 @ March 25 2009, 3:25 PM GMTYeah, but I'd only go and knacker it by including some that I've made up, which nobody ever seems to notice!
I wondered what this "Blackadder" thing was you mentioned earlier.
Cheeky.
Every month seems to be a top x sitcoms on this site. It was favourite, then top 5, then top 10. Can we just get all the sitcoms in the guide, rank them and be done with it. There's only about a thousand. Cheers-thanks 
My top five
1. Frasier
2. Dad's Army
3. OFAH
4. The Office
5. Fawlty Towers
Quote: Lord Meldrum @ March 25 2009, 4:12 PM GMTMy top five
1. Frasier
2. Dad's Army
3. OFAH
4. The Office
5. Fawlty Towers
Hurrah, the doley obsessed with his ex girlfriend's arrived! 
Huh?
1.Fawlty Towers
2.Green Wing
3.Blackadder
4.The Office
5.Friends
6.I'm Alan Partridge
7.Spaced
8.Only Fools And Horses
9.The Young Ones
10.Peep Show
11.Curb Your Enthusiasm
12.Scrubs
13.Extras
14.Frasier
15.The Royle Family
16.Outnumbered
17.The Thick Of It
18.The Mighty Boosh
19.Father Ted
20.Black Books
Honourable mentions: Ever Decreasing Circles, The Smoking Room
If The League Of Gentlemen counts (I'm not having that argument again) it would be Number 5.
My top seven and a half -
Dad's Army
Red Dwarf
Big Bang Theory
Porridge
Reggie Perrin
Scrubs
The You
Quote: shaggy292 @ March 25 2009, 5:32 PM GMTIf The League Of Gentlemen counts (I'm not having that argument again) it would be Number 5.
Alas not!
Although I've no idea how we're going to categorise it on the site. :/