1. Sherlock - The first 2 seasons were top tier television, especially the season 2 finale. But Moffat and Gatiss got too far up their own ass after that, making the show convoluted for convolution's sake. There was a noticeable decline in quality, and now a lot of people shit on you for liking Sherlock.

2. Game of Thrones - The first 4 seasons are the literal best pieces of television. They were done on a relatively smaller budget, which is far surpassed by current era television, even when adjusted for inflation, but none of these shows match the scale and breadth of earlier Game of Thrones. Rings of Power was unable to match a fraction of the quality with an unlimited budget, The Witcher, Halo and House of The Dragon had established lore and stories the showrunners absolutely ignored, even the Last of Us had an insane budget run by a veteran scriptwriter who failed to get the point of Ellie in Season 2.  D&D, with Game of Thrones was able to achieve an insane production, across multiple countries, on a scale never done before, with quality never achieved again for a fantasy show, consistently, year after year, for the first four years - Modern shows would have taken 2 years to give us a half hearted adaption. Yet, because seasons 7 and 8 absolutely shat the bed, the fans retroactively think that D&D never cared about Game Of Thrones. I'm pretty sure no other showrunner would have been able to match the initial quality - They are top tier adapters, they were able to make meaningful additions (Robert's war stories, Varys/Littlefinger conversations) that added to the world, but they did not have the books to go towards the end, and Martin was not able to solve the world's story telling problem after 15 years. They got burnt out/stopped caring at the end, but nothing will change the fact they wrote and created one of the best shows ever.

(Hated trope) Shows with god tier earlier seasons which the fans retroactively hate because the latter seasons shat the bed.