Family Guy has had some hilarious episodes, although maybe not recently. The Simpsons changed animation and television forever, kind of made the FOX network, and remains relevant and still has a pretty decent ratio of funny shows to duds. No comparison beyond them both being animated shows featuring a family. The Simpsons wins.
And The Simpsons has contextual humor and manages to speak to both highbrow and lowbrow sensibilities. Can't really ask for more than that.