The Office and Partridge are the best out there for me, both genius IMO. Gervais and Coogan are great in everything ive seen them do. (Put I'm Alan Partridge on or The Office most nights, never gets boring) Father Ted is just behind though, brilliant.
Blackadder is great as well (think atkinson is very clever with words and his delivery is spot on), Faulty Towers, Monty Python, Only Fools etc.
That arrested development is the closest thing i've seen to really good comedy from america (not counting 'The Simpsons' and Family Guy which are hilerious), friends is funny but the humour is a bit obvious.
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Look out for a new comedy on BB3 called rush hour, seen the first episode last night, quite a good sketch show.