I quit watching South Park over a year ago for the following reasons:

1. Too much 3d and Particle effects.
Seriously, no one watches these kinds of cartoons for special effects. That's what the X-box 360 is for (and this is coming from a Wii owner). I'm all for the use of 3D effects in 2D cartoons when they're used sparingly, but they use them too damned much.
2. Same shit, different current event.
This is why the first three seasons of the show are better than the latest ones. The stories were simplistic and the show just relied on profanity and Kenny getting killed almost all the time. Nowadays, they take any current event and go over the top with it to the point where completely misses the point.
3. Piss-poor jokes.
I'm getting sick of movie references and sight gags as a form of humor. Is it really necissary to spoof indie and mainstream movies every scene? Don't get me started on their sight gags; they're an insult to Tex Avery and Chuck Jones.

Truth is, I respect Trey Parker and Matt Stone as filmmakers; but it's best that they stick to the big screen.