The Simpsons and Futurama are great but they are all repeats. Family Guy is relatively new to TV so it is funnier because of that fact. I do like Brian & Stewy from Family Guy. The dog is always drunk and the baby is always trying to take over the world. Good luck to the little guy
South Park is good but again the repeats get boring after a dozen times.
American Dad is another one to watch. It's made by the same people that do Family Guy and has a few recognisable voices. It pushes the boundaries a little bit and should not be watched by people under 16.
The last one is Drawn Together. It has funny moments but pushes the boundaries too far some times, at least for my liking. Definitely an 19+ show.