No love for Contra? A Contra stage would be awesome. There are many unique stages in that game. My candidates would be the Jungle Stage, Waterfall, and the final stage with the aliens(can't remember the name). Waterfall may be a nice stage to play in, but we already have a Waterfall stage. The Jungle would be awesome, even if it had the exploding bridges. And the Alien stage would be good, even to see the giant alien head in the background.