I don't find the old ones like On the Buses hilarious, just gentle meander and a great record of life as it was - in a time where there isn't much documentary film about the era. Also a record of humour as it was. Still probably better on the whole than the programmes BBC & ITV are choosing to run with these days.
The ones that make me laugh are few - but Father Ted, The Inbetweeners, Still Game, and even having watched every episode numerous times, Only Fools and Horses and Fawlty Towers.