The Simpsons have been one of the most popular TV series on the air for more than three decades. After so long, it might be too late to end the series in a satisfying manner with a definitive final episode that brings the stories of Homer, Marge, Bart, Lisa, and Maggie to a natural conclusion with a real sense of closure.
The Simpsons is by far the most successful primetime scripted series in US television history. It was one of the many valuable assets that Disney acquired in its very costly acquisition of 21st Century Fox. It probably wont let the producers end the series anytime soon. However, The Simpsons has already released a few episodes that would have made a fine series finale.
If this was the last episode, Simpsons fans would have missed out on a lot of great Golden Age episodes, but season 4's Lisas First Word would have provided a heartfelt conclusion to the Simpsons story. As flashbacks fill in the early days of Bart and Lisa's childhood, Bart is initially resentful of the attention he receives, but warms to her when she says her first word Bart and realizes she looks up to him.
Maggie's very first words, spoken in the last segment of this episode, would have been the perfect ending for the series. The show's most heartbreaking, tearjerking moments are paid off with one of the show's most heartbreaking moments: Homer is pretty hopeless as a husband and father, but he loves Marge and his kids and would do anything for them.
You Only Move Twice, a season 8 Simpsons episode, has been hailed as one of the greatest Simpsons episodes ever created, but it also might have been a terrific series finale. Homer gets a job working for a James Bondian supervillain and relocates the family to a new city. Here, he plays Hank Scorpio, a charming megalomaniac who hires Homer as the chief motivation for his corporations nuclear division.
Homer settles into his new career quite well, but all other Simpsons struggle to fit in at their new house in Cypress Creek. This narrative hammers home that Springfield is where the family belongs, which might have been a lovely conclusion to the series.
Summer of 4 Ft. 2 (season 7) may have been the final episode of the series. It concludes the year with a natural narrative conclusion, sending the Simpsons away from Springfield, where Lisa is determined to change her life. It would also make a perfect ending for Lisa's character arc. She chooses a different personality to make friends on vacation, but she ultimately realizes she was okay just the way she was.
Behind the Laughter, the most self-aware episode of The Simpsons, redefines the entire show as a show-within-a-show. In a sharp spoof of the VH1 series Behind the Music, this meta riff would have been an outside-the-box way to conclude the series.
Al Jean said in an interview with former Simpsons writer Conan OBrien that the season 23 episode Holidays of Future Passed was intended to be a possible series end. If those negotiations would not go through, critics agreed that the episode would have been a good ending for the series.
Holidays of Future Passed is a flashback to the future in which Bart and Lisa struggle to connect with their own children. One emotionally captivating scene, particularly a heart-to-heart interaction between Bart and Lisa in their old treehouse, would have made this a perfect series finale. The Simpsons began with a Christmas episode back in 1989, so it would be appropriate to close the show with one.