I was never a big fan of Beavis and Butthead because it was the show all the stoners liked, and I've always had a pretty low opinion of stoners and stoner culture. Still, it can't be denied that the show produced some iconic lines and some iconic moments.
On the other hand, King of the Hill is great. It so perfectly captures suburban Texas culture in a bit of a satirical manner, without being ugly or mean-spirited.
And anyone who's ever worked in a cube farm, especially for a Tech company, has to appreciate Office Space.