I just took a look through the highest selling games in Japan, and the record holder for a Western developed game, is the original Donkey Kong Country with over 3 million units. Tetris on Gameboy is above it, but that version of Tetris was developed in Japan, even if the original was Russian.
NSMB was completely eaten up by the Japanese recently, there's clearly a massive market there for full content 2D platformers, and the series has a history of success in Japan. I think they can do it, and it would be a remarkable achievement if they do (given how 'impenetrable' the Japanese market is supposed to be).
A game I'm developing with some friends:
It is largely a technical exercise but feedback is appreciated.