South Park's brilliance after all these years is astonishing. How they have kept it so brilliant and so fresh is maybe the greatest achievement in television history. It lays the claim to greatest animated series ever, now.
The Simpsons may have had a greater prime, and a greater impact during that prime on the country as a whole, but it hasn't kept up. It's a story that can be told in numbers.
South Park goes 265 episodes deep before any episode falls below a 7.5 rating on IMDb. It goes 292 episodes deep before any falls below a 7.0. The #308 episode, lowest rated on the show, is a 6.3. That means that right now
a whopping 86% of the show's episodes are 7.5+, and 95% are 7+.
https://www.imdb.com/search/title/?...&sort=user_rating,desc&count=250&ref_=adv_prv
The Simpsons gets to 245 episodes before it falls below 7.5. Close. This is a testament to the sheer volume of its greatness. The issue is quality control. See, it has 684 episodes aired so far. This means
just 36% of its episodes are 7.5+. In fact, the bottom 100 episodes are 6.3 or lower. This means the public rates 1/7th of the show's episodes to be as bad (or far worse) than
South Park's worst. It craters at a 3.9! That is one of the worst episodes of tv ever made. The worst episode of nearly every show that gets canceled after just its first season, or sometimes before even finishing the first season, isn't that bad.
https://www.imdb.com/search/title/?series=tt0096697&view=simple&count=250&sort=user_rating,desc
Or, more easily digested, the story told in numbers mapped to a jpeg (not fully updated, it's currently in season 32):
*Edit*
Oh, yeah, you might have noticed the jpeg-maker arbitrarily ranked 8.6+ as a "Great" episode. By that metric,
South Park has 69 "great" episodes. That's roughly 2 out of every 9 episodes of the show for its entire lifespan. With a season length of 22 episodes, the most common for the
The Simpsons, that means it would have 5 "great" episodes every season for its 23 complete seasons so far. Bear in mind
The Simpsons hasn't produced a single episode of that caliber for 20 years, now.