I liked season 1 because that was the moment I got to know the brony community and it was a great start, but after the final episode I felt like the world crumbled beneath my feet. so during the time there wasn't a season airing, so my expectation for season 2 was: it should be as good as the first season, and the first episode should be worth the long wait.
after all season 2 lived up expectations and I really loved Discord so...
when the final episode aired I thought it was the best ending of a season ever.
so:
I thought season 2 was the best season because it lived up to my expectations. and my expectations were based on the last episode of the first season