To tell the truth, I LOVE almost every Nintendo system. But the system I grew up with was the classic NES, not only did it have great original games and 2 player action. But it started most of the best series, such as Zelda, Megaman, and even Mario.
Nice, I can't see any graphical errors or anything like that, I think you should add some bushes in the background because a few of the screens look a bit boring. I like the over world changes, and I also like how you mixed around the title. Keep it up, I'm sure it'll be a good one.
I like it so far, not only because of the SM3 (which I love), but because of your good placement of objects and enemies. One thing I can suggest though is changing the music, I'm sorry but I don't really think the music fits.