[Wikipedia: http://en.wikipedia.org/wiki/Snake%27s_Revenge]
Snake's Revenge is a stealth action game by Konami released for the Nintendo Entertainment System in 1990. The game was produced as a sequel to the NES version of the original Metal Gear, made specifically for the North American and PAL market following the success of the first NES game. However, Hideo Kojima, the game designer of the original Metal Gear, was unaware of Snake's Revenge, and decided to develop his own sequel for the MSX2 computer after being informed of the game's creation. The resulting game, Metal Gear 2: Solid Snake, which was released exclusively in Japan only a few months later, is recognized as the canonical sequel to the original Metal Gear, relegating Snake's Revenge to a non-canonical status.