A time travel based game would be good.

I agree you that SMG is all hype about graphcis, innovation and music but the game itself is meh. Most stars take like 15 minutes to go if you aren't speedrunning, everything is so much slow. The 2D stages were a failure because they felt like you were draggin a stone with you. The finals stage was very cool however, if only every stage was like it. It wasn't a bad game, but it wasn't nearly as good as some people say and is definitly inferior to both DK Returns and both New Super Mario Brothers.

no fair someone already stole everything  I swanted to say! That guy^

This. Koji Kondo did one track for NSMB DS and somehow they thought that would be enough for two games' music? I want a Koji Kondo main theme.

I want a 2D version of Super Mario Galaxy. That would be incredible.

1. Space world, Metropolis world, Theme Park World, Minus World, Big World, Pipe World, and basically anything that is not a desert, water, or ice level.

2. More surprises. LIke when you discover the Sky world in SMB3.

3. New Suits: Super Raccoon/Tanooki Suit - extra long flying time that can be extended in some way. Drill suit, Giant suit, Rock Suit, etc. etc.

4. Endless Skies: For flying, the skies can be infinite instead of blocked off by an invisible wall. As you fly up, random content could be created like cloud platforms, coins, secret pipes, and eventually you could see the sky fade to black as you enter space. This could be the way you get to space world.

5. Endless Ground: The drill power-up from SMG2 allows you to dig infinitely downwards. And in the same way as endless skies, random content in created that you can explore.

6. Some 3d Levels: just like 3d mario had some 2d content, 2d mario should have some 3d content. Not anything drastic, of course (no star finder puzzles please). I was thinking more along the lines of a Crash Bandicoot style level where you have to run away from the screen (like in the e3 presentation if you saw it).

7. Online where each player has their own screen and can separate from other players. Street Pass can be used to exchange high scores, low times, etc.

Many have already said it before me...

It needs to be more like SMW. Thats the perfect 2D platformer. NSMW was very good too, but absolutely not up there with the SNES Marios. 

Super Mario World 3, yes please :D

I won't aknowledge this as a Mario game.

There was only one SNES Mario, and some I don't think many aknowledge Yoshi's Island as a 2D Mario. Even Nintendo doesn't, since they made Yoshi's Island DS without "World"