As interesting as it would be to make a Minecraft clone, a lot of beginners seem to want to jump right into it or get someone else to make it. Have you considered Cube Creator 3D, already available on the 3DS?
@Cameron
Smile BASIC is currently on the eShop in North America. The programs you make with Smile BASIC don't show up on your Home screen; you have to launch Smile BASIC to use them.