My memories of 2004 grow hazier over time -- that was a decade ago, after all -- but I still remember what first drew me to World of Warcraft, and it wasn't a longstanding love of the strategy games. No, what engaged me was the fact that it promised a break from the tedious group-based slogs and aimless wandering that made up the MMO landscape at the time. After playing Final Fantasy XI for two years, the idea of being able to just go out into the world and do things and have actual quests was so intoxicating that it could be legally called a drug.
Personally, I find it almost embarrassing to talk about what first drew me to WoW, because I had no idea what WoW was until the day I picked it up. Despite being a big fan of Blizzard games my entire youth, having grown up playing StarCraft, Diablo, and the Warcraft RTS games, I didn't know World of Warcraft was even a thing that existed until I ended up with a beta client downloading at the behest of some of my closest friends. I have to admit, then, that no quality inherent to WoW drew me to the game. A desire to play video games with friends is what drew me to it. If they hadn't started playing the game, I never would have, either.
World of Warcraft's quality, engaging gameplay and the extended community that appeared around it is what convinced me to leave both City of Heroes and Final Fantasy XI to become a full-time Azerothian, but not what convinced me to visit for the first time.