Selection bias is also apparent in ranking sites for shows where seasons/sequels are ranked individually.

For example in anime, Gintama appears 8 times within the top 50: https://myanimelist.net/topanime.php

It's not because it's a popular show. It's just that people who didn't like the first few episodes have already stopped watching! And it's polarizing enough that the only people who stick around for so many seasons are the ones really love it. So it will get rated a 10 even for mediocre content.