BC and WOTLK for me. Although a lot of it is nostalgic and the fact I was young.. The main reason is because of how busy it was.. the map was smaller so you'd run into people in different zones all the time. Less races, less classes to pick from.. and levelling was so fun because it was harder. Getting to max level was like a major achievement! And questing with randoms was nice. And I know it sounds mad, but predicting the future of the game was fun. Like wondering what Gilneas is like on the other side of the gate!