Terraria kicks Minecraft's ***. Got bored with Minecraft in a few days (I don't think the developers really thought through player progression that well, plus it liked to freeze up on my pc a lot, plus I got a corrupted chunk that destroyed my save, plus I hate having to replace items all the time), but played Terraria through and still go back to it occasionally. It's not free but the $10 is a pittance for the several weeks (months?) of fun and diverse and non-buggy gameplay I got out of it. Plus the custom and adventure maps give you something to do when you've finished. Even was fun to try to restart with nothing from the beginning.