There has been some debate over the last few years about what Minecraft actually is. In short: is Minecraft a game, or an engine to create games with?
On the one hand, Minecraft as a game seems obvious enough: there are things to do, stuff to craft, monsters to fight, and even an end-game goal in Survival, of sorts. Players can (and do) spend countless hours gathering resources to build amazing homes and creations, gear up with the best stuff diamonds can buy, and slay the (proverbial or literal) monster. There is also Creative, allowing people to build whatever they like. Back in Survival, Hardcore is also available for those looking for the ultimate challenge of surviving in a world almost overwhelmingly willing and able to drag Steve down. Triumph in Hardcore is a beautiful thing.
On the other hand, Minecraft has been the foundation for countless creations, and we're just talking in-game, for the moment. Everything ranging from basic mods to improve, change, or otherwise alter the parameters of the game, all the way up to full-blown total conversions, or entirely new games or game ideas, built inside, through, and for Minecraft. From a programmer's perspective, it seems possible to compare Minecraft to game engines like Unity, that allow them to build whatever they like within the system. This is often (though not always) in the form of mods, but both plugins and pure vanilla redstone/command block creations have made their debuts, changing the game in subtle or grand ways. Even putting that aside, Minecraft's open-ended nature lends itself well to customizing play just by changing how one plays it, not unlike playground rules. What a player does in the game is decided entirely by that player, not the game itself.
So, what do you think? Is Minecraft more like a game, or an engine to build games?