Red dwarf peaked imo in seasons 3/4/5. Early seasons were funny because they were new and later were funny to the die hard fans.
Blackadder has always been pure genius. The first series was a bit meh, but if you watched the documentary about the series, they all thought so. I'm very glad they stopped at Blackadder goes forth, any more would have seen it slide and would have been a shame.
Can't fault Father Ted, brilliant doesn't quite describe it.
Both seasons of Phoenix nights are brilliant too. Watching Brian Potter going round the roundabout shouting "Pyschic? whats a pyschic?" comedy gold
Shameless has been a recent favourite too, not the US version, that is plain awful