Nothing dates a show more than griping about politics. That's not to say that The Simpsons has never done it - they have. Just not very often (Politically Inept, With Homer Simpson and Two Bad Neighbours were probably the big ones). Same with topical issues - if you rely too heavily on what's going on in the world for your jokes, their longevity just isn't going to be there. Now, a lot of Family Guy's humour relies on "hey, remember these things from your childhood? Aren't they great/lame!?!" - especially early on - but that basically ensures your show appeals to a specific generation. They've moved away from that in more recent times, but the reliance on current celebrity scandals is still there. It's not to say that it's not funny, but it's more of a niche approach to humour, and there's probably too much of it. It reduces the enjoyment you get from watching the show years later (something we'll revisit later).