A decent list, but Frasier got shafted, as he was definitely top ten material (number one in my own opinion). Gotta disagree with you about Buffy, Zero. I don't even think she was the top character on her show, let alone 13th all time. Rob Petrie was too low, as was Bob Hartley. And finally, too many characters were combined into entries. Sam and Diane together? Shelley Long left Cheers in 1987, and Sam did just fine on his own!
EDIT: And I was glad they included Dick Solomon. 3rd Rock was the most underrated sitcom of the 90s, IMO.