This is a really interesting idea, so I decided to take a crack at it. I’m not too sure how useful this would be for your purposes, because I’m not sure where you consider the drop-off to occur. I definitely agree with most people that the drop off started in seasons 9 or 10, but I still think the show is still pretty decent for seasons 10-20. Personally I didn’t really start watching the show until I was around 9 or 10, which is around seasons 14-16, so I probably have a much better reaction to seasons 10-20 than others. I stopped watching the show halfway through season 21. For me, Season 14, is the last season before the decline had fully taken effect. There are definitely still some really good gems throughout the widescreen HD seasons of the show, but most of my list is from seasons 15 and 16, with a handful of episodes from seasons 17-19 and I tried to find at least 1 from every season of the show after that. I tried to find episodes that tackled contemporary issues, as the show’s best episodes are often ones that tackle semi-serious subject manner, episodes that focus on certain character’s relationships, and those that bring a sense of closure for specific characters. I put an R next to episodes that I’m not sure should be in this hypothetical final season.
1 S15 My Mother The Carjacker (Closure for Mona Simpson)
2 S15 Today I Am A Clown (Closure for Krusty)
3 S15 My Big Fat Greek Wedding (Closure for Skinner and Edna)
4 S15 The Way We Weren’t
5 S16 Future Drama
6 S16 Sleeping With The Enemy (Closure for Nelson
7 S16 She Used To Be My Girl
8 S17 The Monkey Suit R
9 S18 The Mook, The Chef, The Wife and Her Homer
10 S19 The Haw Hawed Couple
11 S18 24 Minutes
12 S20 Sex Pies and Idiot Scrapes
13 S16 There’s Something About Marrying (Closure for Patty)
14 S16 Goo Goo Gai Plan (Closure for Patty)
15 S18 The Wife Aquatic R
16 S19 Eternal Moonshine of the Simpson Mind
17 S19 Mona Leaves A (Closure for Mona Simpson)
18 S22 The Neediest Catch R
19 S23 Ned ’n’ Edna’s Blend Agenda R
20 S31 Thanksgiving of Horror
21 S23 The Book Job
22 S24 The Saga of Carl R
23 S25 Steal This Episode
24 S26 Simpsorama
25 S30 Bart vs Itchy and Scratchy
26 S30 Woo-Hoo Dunnit
27 S27 Barthood
28 S29 Mr. Lisas Opus R
29 S23 Holidays of Futures Passed