This list is not 100% from best to worst.
I have gone on feeling when I is positioning each new anime.
But the whole thing, I see it like this.
PS: Each season of an anime is together and after each other, the first season is at the top of the list and the last season at the bottom. If there is not anything special, but the anime with it's every season is located together in the list even if, for example, one of them should be further down the list.