Family Guy is something I watch as a guilty pleasure. I know it's not brilliant (and I'd say pretty poor if you compare it to, say, The Simpsons when that was good), but it's entertaining. I don't think it pretends to be anything more than it is really and just goes for rather silly and sometimes quite crass jokes, but I'd be lying if I said I didn't like it. I don't go out of my way to watch it, but if it's on I'll watch it.

American Dad I watched a few episodes of but couldn't get into it. Don't know why really. As BoB said, the alien's voice is very annoying.