Arrested Development is probably one of the funniest shows still on the air right now, hands down.
The 500 lb. gorilla that is The Simpsons needs to really call it quits. They've been on and off for the past few seasons, and the current crop of writers doesn't do the show nearly as much justice. This was the first year I barely watched any episodes and didn't really miss it.
Are we talking specifically sitcoms or comedy shows in general? If it's the latter, The Venture Bros. is the best thing to hit the airwaves in the last year.