I do think there is kind of a "perfect storm" effect around this game. It isn't so unique that you can't find a game to compare it to. In fact, two of the biggest influences are already present in Notch's previous work:

Procedural landscapes: Infinite Mario Bros.

Multiplayer wilderness survival: Wurm Online

And the voxel terrain concept - the feature which surfaces most visibly - was already demonstrated in many other games.

In light of this I've charted a path for my own games which doesn't seek to ape the specific concepts or technologies of Minecraft, but instead aims to achieve the same level of intrinsic "I want to share this" and supplements it with a dynamic that adds some explicit rewards for doing so(the social game virality model - not necessarily tied to FB or any "social platform" though). This comes at some risk of sucking out the intrinsic joy, but the potential reward is to have even faster growth than Minecraft - assuming the game is equally good.