EE, you insult me. What's with these softball questions?
American Dad and Futurama, respectively. Although both have been slipping in recent years, as is the case with almost every show that runs for more than half a decade, unfortunately.
I will say that Family Guy is the only one out of the four that I just absolutely can't stand anymore. The Simpsons is but a wisp of a shadow of a ghost's dream of its former self, but it at least still features characters that I do not actively dislike. Family Guy has become absolutely painful to watch. That show badly needs to be put down, for the good of animation as a whole.
Disclaimer: Bob's Burgers isn't, like, great. Don't get it twisted. But, like J, I had extremely low expectations for it before it debuted and it has surprised me pretty consistently ever since, to the point that I would recommend it to someone who hasn't given it a chance yet. The kid characters on the show, I think, are the meat of it (no pun intended, I'm just that dope). It's still mainly driven by the adults most of the time, like pretty much every other animated family sitcom kind of show, but the child characters are a lot weirder and funnier than most child characters are, and they help push plots to places you wouldn't expect (the oldest daughter, Tina, especially. I actually don't think I've seen a character quite like her on a mainstream cartoon before. She has sexy time dreams about zombies; no joke). Compare that to a show like Family Guy, where Chris is useless as anything other than the occasional Herbert The Pervert setup, Meg is only ever used as a walking punchline (for no real reason!), and Stewie's shtick has been milked dry multiple times over. The kids in Bob's Burgers are much different, bolder types of characters so, if nothing else, you can at least expect them to do stuff that will occasionally surprise you.
It's worth a glance if your curiosity has been piqued at all. Also, it's got John Benjamin voicing Bob, and I just love hearing him talk.
How did I talk about that for so long what am I doing where am I