I think there are some misunderstandings about Minecraft floating about. Let's have a look at minecraft.net's
About the Game:
I strongly believe that all good stories have a conflict, and that all good games tell a good story regardless of if it's pre-written or emergent. Free building mode is fine and dandy, but for many people it will ultimately become boring once you've got it figured out. It's like playing a first person shooter in god mode, or giving yourself infinite funds in a strategy game.. a lack of challenge kills the fun.
For survival mode, I'd rather make the game too difficult than too easy. That also means I'm going to have to include some way of winning the game (or some other climax) to prevent it becoming too exhausting.
This is reflected in the updates lately (if you follow them) -- experience points, skill trees, achievements, and
hardcore mode (when you die, there's no "load" or "respawn" -- the world gets deleted). "Creative mode" is like playing with LEGO, but "Survival mode" is where the
game is at.
More on topic (or on the topic of this tangent lostclimate started) -- to me, "what makes a game" is interactivity. It's the defining feature. AAA titles often strive to be more and more "cinematic" -- more and more like movies. This is generally a bad direction to go in (but can be OH-so-good if you get it right like the Uncharted series tends to), but they're still games. You could have a movie with a "choose A or B" right near the end as the only interaction, but it'd still be a game (albeit an awful one -- no matter how good and satisfying the story is, people will deride its limited interactivity).
Regarding whether or not a game should or shouldn't have a defined ending (Minecraft as it is now, LEGO blocks, playing in a sand-pit, VS most other games), I don't think one is inherently more fun than the other. Having a goal will have the player finish satisfied, while having no goal will have the player finish tired of playing the game (or dragged away kicking and screaming by friends for an intervention), but the latter game often provides dozens of hours more fun than the former.
