Needs a lot of work.
Particularly your hit detection and collision response. I know it's not easy, I still hear complaints of "the frogs killed me when I wasn't even NEAR them" in my platforming game, but when I hit the turtle's a little too much to the side and somehow get moved about 150 pixels to the left (much further away from the turtle than I should) and therefore miss a platform, you know there's a problem.
Also, if you're going to rebuild a game almost carbon copy, the game should feel the way the original does. Koopas should leave their shells, Mario should bounce appropriately off enemies, pirahna plants should stop coming out of their pipes when you're standing right next to them, etc. Without these, the game really felt stiff, and it would have been more worth my time to play the original that's sitting five feet away from me than play your alternative.
Nice try, but you still have a lot of work to go.