So what would you score it if it had the optional discovery?
That's always a really tough call. Maybe an extra .5 or so? Far and away the biggest killer of this game for me is the world size, because it so limits the scope of what the game is. Had world size even been, say, four times bigger than it is now, I still would have found it small, but I think I would have given the game a decently higher score.
More on this below...
That goes back to "I liked it this way on the PC version" and "it affects an aspect I enjoyed in the PC version" instead of thinking about "how well does this work in the 360 version".
Games don't live in a vacuum, and while I think you always have to take a look at each game from what it is and what it's trying to be, the PC version of Minecraft still exists, and the XBLA version of Minecraft is still a port of that game (or, at least, I'll argue that point until I'm blue in the face).
And again, completely putting aside the PC version, the world size in the XBLA version of Minecraft is
too small for the XBLA version of Minecraft. In the first couple of hours, you may not notice that fact as much, but the more you play, the more apparent it is that it's just so ridiculously small.
My comment on LEGO and building on only one baseplate really is a fitting analogy I think. Yeah, you can make some amazing creations on that one plate—but it also really limits the reaches to which you can take your imagination. You don't have to have owned 200 baseplates before to say "using just one baseplate feels too limited for what I want to do." And that's just looking at things from the creation side, and not the survival/exploration side. Both of those take a clear hit due to world size as well.
So, sure, item discovery is a shame (to me), and I think players would have a better experience with the option to decide if they want things spoiled or not. But far, far bigger of a problem is the world size.
But for some people, they won't care! And that's great. I'm just really sad how compromised this version of the game feels.