IMHO the best and the worst episodes of each season (in bold — the best and worst of overall series, upd. 15/12/20):
1. Moaning Lisa/Some Enchanted Evening 2. Bart vs. Thanksgiving/Itchy & Scratchy & Marge 3. Mr. Lisa Goes to Washington/The Otto Show 4. Homer’s Triple Bypass/Selma’s Choice 5. Secrets of a Successful Marriage/Homer the Vigilante 6. Two Dozen and One Greyhounds/Lisa’s Rival 7. Home Sweet Homediddly-Dum-Doodily/Homerpalooza 8. My Sister, My Sitter/The Homer They Fall 9. Miracle on Evergreen Terrace/Bart Star 10. Wild Barts Can’t Be Broken/Monty Can’t Buy Me Love 11. Days of Wine and D’oh’ses/Pygmoelian 12. Homer vs. Dignity/New Kids on the Blecch 13. Poppa’s Got a Brand New Badge/Weekend at Burnsie’s 14. Moe Baby Blues/Helter Shelter 15. Fraudcast News/Co-Dependent’s Day 16. Goo Goo Gai Pan/A Star Is Torn 17. The Seemingly Never-Ending Story/Marge and Homer Turn a Couple Play 18. 24 Minutes/Treehouse of Horror XVII 19. Eternal Moonshine of the Simpson Mind/Husbands and Knives 20. Coming to Homerica/Treehouse of Horror XIX 21. The Squirt and the Whale/Treehouse of Horror XX 22. The Blue and the Gray/Elementary School Musical 23. A Totally Fun Thing That Bart Will Never Do Again/Moe Goes from Rags to Riches 24. Hardly Kirk-ing/Gorgeous Grampa 25. Brick Like Me/What to Expect When Bart’s Expecting 26. Sky Police/Treehouse of Horror XXV 27. Halloween of Horror/Treehouse of Horror XXVI 28. 22 for 30/Havana Wild Weekend 29. Flanders’ Ladder/Springfield Splendor 30. Baby You Can’t Drive My Car/The Clown Stays in the Picture 31. The Way of the Dog/The Incredible Lightness of Being a Baby
The Simpsons season ratings:
1 > 2 > 4 > 7 > 3 > 6 > 8 > 5 > 27 > 21 > 9 > 12 > 20 > 25 > 29 > 10 > 17 > 26 > 24 > 15 > 18 > 13 > 14 > 28 > 19 > 31 > 30 > 16 > 23 > 11 > 22
I think that thoughts may differ, because so many people, so many opinions.