IMDb ratings can be strange things. Determined using a weighted average system, it means anyone who is a registered user can vote but not all votes are equal, and despite the flaws it stands alongside Rotten Tomatoes and Metacritic as a solid, quick gauge of something's quality and popularity.
It's more well known on the movie side of things - the clue is in the name and all that - and its IMDb Top 250, whereupon The Shawshank Redemption has held the number one spot since before the dawn of time itself.
However, dig into the TV side of things and you can find just as many weird and wonderful statistics. For example, of the three top-rated series - all of which currently hold a 9.5 score - two of them are fronted by David Attenborough, with 2006's Planet Earth and 2016's follow-up Planet Earth II picking up the plaudits. Indeed, the top 10 also includes 1980's Cosmos (9.2), and it's long-time-coming sequel Cosmos: A Spacetime Odyssey (which arrived 24-years-later and has an even higher rating of 9.3).
Across all of the most popular TV shows from before, during, and after the Golden Age there are ratings to that will delight some fans, infuriate others, and all of which are really quite surprising.