YES!!!! More content the better. 

I disagree entirely. Maybe that's true for regular 3D games, but definitely not true for the cubic tileset of 3D World/Land. It would be just like Minecraft in that regard.

If there is a company that can spend enough efforts and talents to cause miracle in that department, it is Nintendo.

http://dreams.mediamolecule.com/

http://modnation.playstation.com/

What I want is a 3d world 2 or another 3d mario by Nintendo. After playing SMM I think I've had enough of "do it yourself" kind of games.
Do you think a 3d world maker would be a good idea? I thought the same and it's been a dream for me for so many years. God I'd buy it if it was good! But after playing SMM all I can see are a lot of levels where you die like a hundred times because there are a thousand goombas flying around, a lot of auto levels, or levels where you must jump from a tiny platform to another for 3 minutes and if you don't jump at the exact time you fall into a pit and die, because the whole level would be a huge pit.

My hype for SMM died like 4 hours in. And I was expecting the game to be almost infinite for me.
Maybe the problem is mine and I shouldnt have hyped the game so much haha.

Edit: Oh! And knowing Nintendo you would only have like 4 or 5 types of platforms to build your levels. Which was one of my biggest complaints with the game the lack of different platforms and enemies (and the background too).

I am a Playstation go through and through but to compare Modnation and Mario Kart is crazy lol

He probably wants a game with good gameplay. ;)

With all due respect to LBP, as a platformer it's pretty terrible.

Won't happen.

It's true for any and every game.  Adding another dimension simply makes things objectively more complicated.  The demands of a platformer are different than the demands of something like Minecraft.