Shantae was a beautiful sidescrolling game that got released near to the end of the GBC's lifecycle, causing a lot of people to miss it. The art is seriously impressive and undoubtedly pushes the GBC's technical limits. Mapping it may be a bit of a challenge since the game employs a real-time transition between day and night which changes the maps' asthetiques and also reveals "fireflies," secret collectible items. Here's an illustration of the world-map (not in-game)
http://media.ignimgs.com/guides/guides/15286/images/MapAncient.jpg
http://media.ignimgs.com/guides/guides/15286/images/MapAncient.jpg