I'd have to say Community, which is certainly the cleverest and most unique, but with any one episode it could be surpassed by Parks and Rec or Modern Family.
Last year I would have said Modern Family, hands down. But I think it's remained in place while the other two have continued to get even better.
One that I haven't heard mentioned here on AT but that I've taken a liking to is
Happy Endings. The writing is often excellent, and the cast is great. All three female leads do a great job: Casey Wilson, Elisha Cuthbert, and Eliza Coupe.