I actually have a graph for this
Season 1: 4 good episodes (Bob gets caught is the best example),5 mediocre episodes (The family-picnic episode,same thing),4 poorly aged episodes (the babysitter episode,same thing)
Seasons 2-4: The first rise,where the Big "Golden Age" starts. Episodes such as the substitute teacher voiced by Dustin Hoffman,Milhouse's girlfriend,Bart failing miserably despite his best efforts [Even Nostalgia Critic
couldn't say anything about it), Krusty's father,Kamp Krusty were nothing short of iconic,hilarious,and at times quite deep. Season 2 I'd give a slight lead to since it had to deeper episodes.
Seasons 5-6: Most people either loved these or hated them,had the series stopped at 10 I'd consider these the worst for being very nonsensical or a little too
political.But because of how most seasons past the 10th turned out,they retroactively count as the Golden Age. That said most were watchable
Seasons 7-8: The absolute pinnacle,with Ned Flanders finally flipping it, the relationship of Bart and Lisa explored in the ice hockey episode, Sideshow Bob's brother,I'm really not sure if there was an episode I could hate during this part. It was like Season 2 except funnier,it was like 5-6 except more intelligent
Season 9: Pretty much like Seasons 7-8 except wackier and at times a little bit too edgy [Sorry that finale with naked Homer and naked Marge left a bad taste in my mouth]
Season 10: The favored love-child of Season 9 and Season 5,usually pretty good stuff such as Bart the Mother
,but occasionally it favored gags over depth,but it didn't take the political route like 5 or 6,it took the Saturday morning cartoon route,if Seasons 7-9 assured there'd by no more wackiness after the damage 5-6 did,10 just resurrected it. The Tokyo episode should've been the penultimate episode and the whole darn series could've ended with the MENSA episode,I mean what better finale than Stephen Hawking pointing out how fruity the place is and punching out Homer?
Seasons 11-12: The worst set of seasons since the very first,which to be fair was sorting itself out. I don't need to say more about this set,Homer even ran over an alligator to match.I pointed out the good episodes,but they were far and few.
Seasons 13-18: Mostly mediocre and corny,the odd seasons kept competing to be worse than the 12th while the evens seemed to be apologizing
Season 19: The first true rebound,the first season with more hits than misses,and frankly the "Kil Gil" and "Mona Leaves'a" episodes were truly something and the finale was really phenomenal
Season 20: The worst season,19 is a diamond in the rough since the 10th apparently since this is just as wacky as the 11th and 12th,except loaded with outdated references and cornier,no self aware-ness either which helps,it got better once it went HD but that was towards the very end,and the damage was done
Seasons 21-22: The second rebound,and definitely rivals to the "Golden Age",but since the show is so removed at this point,and could be considered a different show,this should be called the "Silver Age" with 19 lumped in and 20 kicked out [for sucking worse than the 12th,...how did that happen
I can't comment on last years or the upcoming one,but I do hope if this isn't the last it's the 25th,because I'm done after the next nosedive.