The CHEERS intelligence graph

Compliments of Neatogama.com.


As someone who wrote these characters for nine years, this would be my order:

Lilith
Frasier
Diane

(now comes a big drop)
Sam
Rebecca
Carla
Norm
Cliff

Coach
Woody
 
Sam was dumbed down over the years but at least during the first few seasons he was very smart and savvy.  So if you average his IQ over the seasons he still comes out way ahead, certainly better