The way it worked is this. The first season was pretty terrible, but it got progressively better over the next two seasons. Then the fourth season was the first that was hilariously funny. And it stayed real funny for a while. It was good until about season 11 or 12 where it was really crazy and gonzo and fun. Then it fell off the map for a little bit. and for years I didn't really watch it. and it kind of sucked. but I've watched a few of the new episodes in the last few weeks, now that I've got a DVR, and they've actually been pretty funny.
Maybe I'm just more tolerant to the show now, since I haven't really watched it in years.