What kind of game would you create in this situation?

[The Ghost of RubangB]

I'd create a level editor for Super Mario Bros., that lets you combine level design elements, items, and enemies from SMB1, SMB2, SMB2USA, SMB3, SML, SML2:6GC, SMW, and NSMB.

You could trade levels to friends with friend codes, and submit them to Nintendo, and the best would be shared. You could make them hours long and save them all to your hard drive. You could make a level that's miles and miles long with 30 save points, or a million short levels into an entire game.

It would be heaven. Nobody would ever make a platformer again.