Warcraft (the strategy) was one of my first games ever and being very easily impressed kid with a soft spot for fantasy, I immediately fell in love with it and its characters. WoW itself was not my first MMO, I played Ultima, Lineage and I think Everquest before it, coming to the game in late-ish TBC.
What immediately striked me was how close the game was to the original strategy in terms of atmosphere - voice overs, icons, models of mobs, NPCs and scenery, all that. It was a world of my favourite strategy coming alive on my screen. Admittedly, as a player I sucked quite badly back then, my guild didn't even wanna see me in dungeons, haha. That's when I opened a world of PvP for myself and got immediately sucked in. Hours long Alteracs, vicious fights at Arathi Basin or Warsong Gulch, all that.
I left sometime around the first patch of Cataclysm - I think I didn't even reach 85... and returned on a new account with a friend who hadn't seen WoW before in the Throne of Thunder patch of Pandaria. That experience was amazing for both of us - for her as a new player, for me as returning player who had seen revamped Cata locations for the first time. About that time both of us also started reading the WoW books and were impressed with just what a huge amount of lore the game has, not without frustrations at what has been done to it at times, of course (I'm looking at you, Kael!).
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So, to sum it up, I'd say that for it is lore first and foremost and secondly that WoW has a lot to offer to any kind of player - casual or hardcore, PvP or PvE, "kissing squirrels" aka achievement hunting, pets, transmogs, etc.
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