I hope the graphics don't suck, like they do in Minecraft. I know it sound superficial, but graphics do matter. Minecraft succeeded despite its graphics, not because of them.
Consider the common complaint about current-day Lego blocks: "Legos used to be simple." You can say that it applies only to the functional aspect, shape, but I think it also applies to their visual aspect. I mean, how many special blocks does Hogwarts or Prince of Persia really need?
And, disregarding all of that, there's a significant portion of gamers out there who will pay in both money and loyalty when you evoke nostalgia, which Minecraft does via pixellated graphics.
While it isn't aiming for all the same points, and is obviously inspired in some parts by Minecraft, I think for example Cube World is a much better looking game. http://wollay.blogspot.co.uk/
Firstly the game is written in Java and hogs enough CPU/RAM as it is. If they had started making high quality assets they would have had to maintain that standard throughout which would have made it much more difficult to iterate quickly which is something that minecraft is all about.
I think of it like Lego , Lego kits are nowhere near as pretty or detailed as other proper model kits but they allow many different possibilities.