That first world is a pretty neat idea, and it was one of my favorite levels, but it:

A: Is extremely easy

B: is bland to look at

C: has bland music

These three complaints can be used for almost all of the levels you posted, as well as the majority of the game.

Now there are a few gems in there, 3D land had a few levels that made me smile, but lets talk about why the structure of 3D land is damming. 

Mario 64, Sunshine, and the galaxy games are structured pretty similairly. You are thrown into a level that changes on each mission you do. Each mission contains an objective that upon completion rewards you with a star.  The objectives are wide ranging, and are not just "get from point a to point b". 3D land has one type of level "finish the level" the levels are almost always linear, there is no misison variety, no huge levels to explore, no time to just mess around and be mario. In sunshine, one of my favorite things was just roaming around the amusment park. I found all sorts of cool things. On occassion, you can even find secret stars. It gives you a sense of freedom that 3D land discourages. That's fine for 2D mario, but it's not at all what I want in 3D mario. 

3D land is also bland as hell to look at. I mean, I didn't know so little imagination in asethetics passed for a Mario game these days. All the while making my ears hurt with it's boring soundtrack.

Then the solution would be to not collect that power-up. Or are the levels explicity designed to require the use of the cat suit? But anyway, I am glad to hear that you enjoyed playing as Bee-Mario in the Super Mario Galaxy games.

Don't you think that other companies would copy Nintendo, if it were as easy to make such a game as you say it is?

And not taking such a risk is bad for what reason exactly? I can guarantee you that a lot of people would sing a different tune, if we got Super Mario Galaxy 3. "Why change a formula that worked?" and the like. The reason why it is a problem here is that we got a game they didn't want.

The point is that SS is a 50 hours adventure game and that Mario 3D world is a platformer.

You can judge 50% of how a platformer is going to be on the first trailer.

People knew Mario Galaxy would be awesome for the first trailer, they knew DKCR would be great as well. You can see that Mario 3D world will be average and can't be great.

It seems to me, you have made your mind this is going to be bland game. Nothing will convince you otherwise. Personally, I am going to enjoy it because 3d land was amazing. I am very confident there are many people in the same boat as me 

"And not taking such a risk is bad for what reason exactly?" You're kidding me? You can see and read the risk right in this thread! The back lash is quite big. Not innovating Mario is ALWAYS a big risk. That's why NSMBU isn't doing too well, and why NSMB2 is tracking BEHIND SM3DL - which, as it happens, DID take a risk in game play! Nintendo fans WANTS innovation in their Mario games.

I think quite a few people would be disappointed in Galaxy 3 as well. The thing with a new 3D Mario is that it always introduces something new; SM3DW didn't. And the problem here is that SM3DW is a follow up to a handheld game. You HAVE to see the issue here!?

I just wanna make this clear: I don't think SM3DW is a BAD game - I think it'll be good and all, and I hope they make this a new spin off of Mario, but a new 3D Mario on a new Nintendo console needs to be something else than this.

I'll adress your second to last paragraph first. After using the same structure for the past four 3D Mario games, with increasing production values for each title, I understand wholeheartedly why EAD Tokyo would try make some major gameplay changes. Previous games had levels that were large, potentially confusing, and didn't always have a clear objective, which made them less accesible than the 2D entries. Super Mario 3D Land breaks down that barrier altogether, bringing the focus back on the platforming as opposed to being a fun tech demo for the 1996 3D revolution. Not that the old formula wasn't great. It simply felt played out to the development team (Mario went to space twice - where do you go from there?).

That's my problem at least, I don't want it to be more accesible. Mario is already pretty damn accesible. Treating my like I don't have any idea what I'm doing made me hate the game. Now I agree that at some point the formula has to get mixed up, and Nintendo had two ways to do it. 1. Make the worlds much bigger, more freeroam, more secrets, more stars. Or the 3D land approach: Small simple levels that guide you to a goal with little to no secrets or freedom. It really angers me that they went with the second choice.

Well, actually, 3D Land became a tech demo for the 2011 stereoscopic 3D revolution, didn't it? And that explains many of the aestethic and structural choices in the game, once you really think about it. Instead of going for a high-detail approach, EAD Tokyo chose to channel Super Mario 64 and Super Mario Bros. 3, two games that directly inspire the gameplay to the point where 3D Land seems like a mashup of both. The rectangular blocks that were once a sort of platform in SMB3 made a full 3D debut, and are very present throughout the game. Some gameplay elements from SMB3 and SM64 return for a few levels. Airships, tanookis, and more are interpreted into 3D for the first time. Heck, the homage to Super Mario 64 and Super Mario Bros. 3 is even apparent in the music, with the main theme paying tribute to Bob-Omb Battlefield.

I would say the 3D hurt the game more than helped it. They were so focused on making the 3D usefull, that they forgot to make some of it fun. It bothered me to say the least. I play Mario games to have fun, not to see why 3D is good. Really I would say 3D land has almost nothing in common with 64. 3D land is far more a 2D game than a 3D one. Everything you do is straight forward. There isn't much of anything other than straight in 3D land actually.

When you think about it as a game meant to channel the past as much as possible, I think the presentational choices are more easily understood (or forgiven). It's bland, because it could hardly be more "Mario" if it tried. But as I was about to say in the previous paragraph (I can't seem to structure my paragraphs properly right now), the 3D presentation dictates quite a lot. Levels are short and quick, because staring at 3D images for a long period of time is probably not a good idea. Levels are mainly linear, with a fixed camera, because it's significantly harder to do anything decent with the 3D effect otherwise. And it coalesces neatly into the handheld design, since the 3DS doesn't have a second stick to control the camera. The question is whether the payoff is worth the changes. I enjoyed the levels where EAD Tokyo tried really, really hard to sell the 3D effect, but to me the best parts of the game were born from focus on bite-sized nuggets of smart design. It probably would've been just as fun for me without 3D, but there you go.

Why does 3D land get to be bland, but no other 3d mario game gets that pass. Each Mario game has brought something new asethetically to the table. 64 looks entirely different from it's predecessors, Sunshine looks wildly different from any Mario game, and the galaxy games both have a style not seen in any other Mario game. How does just saying "It's ok that it's bland because it looks like Mario" give it a pass?  Now I don't think that a traditional 3D mario game would have been affected by the 3D affect like you said, but if linear levels are truly good for 3D, why does 3D world get to be the way it is? Hell, it's not even on a handheld, and yet it's somehow ok to have fixed camera linear levels.

Now, this leads us to 3D World. Truth be told, I don't know if the game is going to be as ingenious as EAD Tokyo's previous 3D Mario games. The best design aspects I've seen from the trailer are what appear to be larger levels and the return of reversible platforms, because they will be even better in a multiplayer context. Graphically, the game aims for higher texture detail while retaining many of 3D Land's existing elements. Really, I don't know what to think yet, but I'd like to get my hands on the game just to see if it clicks. I know I didn't completely "get" 3D Land until I was knee-deep into it.

My problem with 3D world it feels in every way like it was made for the 3DS. It has those shorter timed levels, it's built with fixed camera's which was made to help the 3D effect, it has midi soundtrack because why orchestrate a soundtrack for a handheld game right? I didn't even like any of this stuff on a handheld so why would I like it now?

Galaxy forces things on the player. This is good.
3DL and 3DW give players the choice. This is bad.

I like your line of thinking...

And yeah, Sonic will totally outdo Mario, because it has yet to be the case that initial impressions of a new Sonic game are far better than the final product.