Above is the actual path that a player takes while play Super Mario Bros 3. The guy who came up with this who goes by the username ahefner has cleverly made a way to build a gameplay automap while he plays. These could be used as a guide for future users who want to know the proper way to play a particular side scrolling game. Super cool.
To see the full map and to get more information on how he did it check out the NES Timelapse Hack.