I'd likely put Vanilla and TBC a bit higher, because they truly captured the feeling of the world - there's all these different races and classes doing cool things - like the warlock igniting the ground beneath his feet, the druid running through the forest and changing shape. It really feels like WoW.
Additionally, I began playing WoW in December when the rumors that a virus was circulating began. I think I'll keep my distance. I installed the game to test whether it was worth the level 20 cap. I was HOOKED when I first saw the BFA film. I was a rolled horde since Sylvanas in the Horde line was extremely hyped.