Which show has a higher percentage of good episodes?

[I spent the winter writing songs about getting better]

The Simspons has 25 seasons, of which 10 were good and then had two that were kind of split, so that equals about 11 good seasons (actually the decline had already begun around season 9, but we'll count it as good here). That's 44% good episodes roughly. Family Guy has over 90% good episodes. Family Guy wins by a lot.

[I spent the winter writing songs about getting better]

Icon of the 20th century you mean. Because in the 21st century it's CRAP.

[I spent the winter writing songs about getting better]

As I say about every fourth time BRTD brings it up (which means I've done it about 14 times), FG is a fine show.  It's not great, but fine.  Good jokes....not much else.  But to compare it to the top mainstream adult cartoons is just silly.  It's not in the same league as KotH, Simpsons, Bob's Burgers or South Park.

OK this is pretty ridiculous, especially with the last line. Now I'll give you the benefit of the doubt and assume you only mean 20th century Simpsons with that bit, but you mention South Park. That mention is a disgrace and insult not only to Family Guy, but the other shows mentioned. That show is f[inks]ing garbage. It's not merely mediocre, or simply inferior to Family Guy, it's completely worthless nonsensical trash. The idea that it's on the level of Bob's Burgers (which I'm not even a huge fan of), King of the Hill or classic Simpsons (!!!) is absurd beyond belief. Hell I'd say that even comparing South Park to Dora the Explorer would be an insult to the latter.

[I spent the winter writing songs about getting better]

Whoa!  You don't like South Park?  First I'm hearing of it.

He thinks that Matt Stone and Trey Parker are a couple of hard-right libertarians and thus South Park is trash. 

I don't understand it either.

It's not just that. The show is painfully and horrificly unfunny and extremely f[inks]ing stupid.