I was being a bit hasty saying most, but it's definitely not the other way around as you say. Probably in between would be a fairer better definition. Some very popular worldwide hit series like Lost, The Walking Dead, Game Of Thrones never topped their first season overall quality and enjoyment wise.Wrong way round. Most shows top their first seasons, otherwise they would die pretty quickly.
What sometimes happens for some shows is that their first season is their best. New BSG might be in that category (although it would be hard to argue against Season 2 of that show). WestWorld might be another one of those. The 21st century tropes that became fashionable over the past half decade became very apparent by the end of season 1 which is probably why I haven't bothered with season 2.
Another series True Detective while not a massive hit or that well known the first season was awesome. The second season crap and the third season while ok above average was trying too hard to be as good as the amazing first season.
The rebooted Battlestar Galactica is one of my favourite sci-fi series even though the last couple of seasons were a mixed bag. Season 1 was stellar and some parts episode's of season 2 (not all) were as good or better for me personally. The mini series that came before the reboot was also very good laying the foundations.
Although based on different source material You could tell in season 1 Westworld the producers etc had been inspired by parts of the earlier BSG reboot. Influenced from the whole who's a Cylon suspense in BSG, was still good season 1 Westworld but that similar scenario had already been done before and better in BSG.