Season 8 was the last consistantly good season. Season 9 was mostly good, but it was the first season I'd give two "Fs' to and Homer was becoming an ass, instead of the slow, grumpy loveable oaf.
When Scully took over, he beat the show to death with his Homer show antics and when Jean took over, Jean's been injecting the Simpsons corpse with drugs. To his credit, he's doing a better "Bernies" to the Simpsons than the guys were doing to "Bernies" in "Weekend at Bernies".