Hi, I recently hacked "Milon's Secret Castle" and made it into a Mario game. (I hope this hasn't been done before.. if so, sorry.) Of course it's not the same thing as a real new Mario game, but you might get a kick out of it. So if you're into NES emulation, feel free to check it out..
http://members.cox.net/defgav/msc/mario.htmlthanks