The IT Crowd. Screw TBBT and its dumb forced humour, The IT Crowd is miles better, but like too many British sitcoms it was canceled too soon.
As good as it was, it's not bad that it was cancelled like most "british sitcoms". It's just we Brits tend to want to end series on a high without forcing another load of episodes out of it until it just simply isn't funny any more (i.e. Family Guy, The Simpsons etc.) I'd rather 4 seasons of quality than another 4 seasons of below-par rubbish when the producers can work on something else!