I can't believe we're onto page 2 of the thread and nobody has mentioned Still Game!
70s: Porridge, Fawlty Towers, The Good Life, Open All Hours
80s: Only Fools & Horses, Blackadder
90s: Alan Partridge, The Day Today, The Vicar of Dibley, Father Ted, Spaced
00s: The Office, Peep Show, Gavin & Stacey, The Inbetweeners
10s: Fleabag, Friday Night Dinner
Generally I don't do American comedy though two of my favourites are Curb Your Enthusiasm and I also loved Frasier.
A shout out too for Minder which wasn't really a comedy but certainly had some funny moments in it - was one of my favourite programs growing up.
My top 3 though would be Still Game, Blackadder and Fawlty Towers.