Quite possibly the most famous unreleased game, StarFox 2 was completed and ready to go when it was cancelled. Nintendo had shown the game at various trade shows and it would have no doubt been a hit. The impending release of the N64 killed StarFox 2 as Nintendo ultimately wanted to push 3D on the N64 and not the SNES.
Many of the ideas present in the later StarFox games were introduced in StarFox 2 such as the transforming Arwing and the tactical map. Finally this lost masterpiece is completely playable on your SNES!