American Dad doesn't even involve Seth anymore (outside of voice work, it's written entirely by a completely different staff), and it shows. It's a fantastic show because it's an adventure comedy which is so lacking anymore.
Cleveland Show has good jokes, comparable to the one or two Family Guy delivers. But Cleveland can't find it's voice, it was supposed to restore the "family" and "one plot" sense of early Family Guy, but it lost that faster than anything ever and now is just the Family Guy with a black guy and a bear clone we all thought it would be.
Family Guy was a good show when it mocked the conventions of a standard 70s/80s sitcom while throwing in stupid references/set pieces that got a "this is stupid LOL!"
Old Simpsons, KOTH, Old South Park understood this. Ground the plot so you're forced to deal with and make jokes within it instead of dismissing it to make bad jokes.
Also to note real quick, KOTH was not entirely axed for Cleveland. KOTH got way more chances than it deserved ratings wise and was allowed a chance to write its own finale. (And will get a burn off on Adult Swim.) Writing was on the wall for KOTH (which might be the best animated series ever) but it lucked out when everything else FOX threw out bombed and so it was allowed to return and DELIVER with some epic seasons that made up for the former "last seasons" but everyone knew it was going away. Threads for FOX's Animation Domination on various forums made that clear, KOTH's half hour was mostly silent except for some smart people, while Family Guy was full of

for even the worst jokes.
The Goode Family deserved at least a second season though.