You have two distinct directions here, though: World of Warcraft's gameplay is rather complex (compare the image of WoW with this image from Minecraft: http://imgur.com/lQdye.png), is about killing monsters and obtaining the best equipment, showing off how much time you're able to spend in-game. I think showing your personality to others is really hard in WoW, at least without talking to them.
Minecraft, on the other side, is about you, your personality and creativity. You're able to modify the game as you like: First off all, you're making your own world! Second, texture packs are available, in order to change both the world and your own character. By making the game less complex, it is also very easy to get into, compared to WoW.
(I'm sure there are other reasons as well, but I'm no professional game developer.)
Minecraft, on the other side, is about you, your personality and creativity. You're able to modify the game as you like: First off all, you're making your own world! Second, texture packs are available, in order to change both the world and your own character. By making the game less complex, it is also very easy to get into, compared to WoW.
(I'm sure there are other reasons as well, but I'm no professional game developer.)