Metal Gear was released on December 22, 1987 in Japan.
There are several differences between the Famicom port of Metal Gear and the original MSX version. The beginning of the game is totally different - in the Famicom version, Solid Snake parachutes into a maze-like jungle area, whereas he directly infiltrates the enemy building in the MSX version and deploys by sea. The Famicom game is overall a lot more difficult, some buildings have been shuffled around as well as items and weapons, and some events are a lot more random - trucks transport the player from one location to another, and the jungle phase loops in many places. Enemies could also track the player down beyond the visited screen and this feature was removed from the Famicom port. The most notable difference is also the underlying goal of the game - players had to battle the Metal Gear itself at the end of the MSX version, whereas they had to destroy a Super Computer which controls the Metal Gear in the Famicom port. Finally, in the North American and European versions, many of the character names were changed - Big Boss became Commander South, and the enigmatic leader of the Outer heaven secret army was given the spoof name 'Vermon CaTaffy' (pun on Lybian leader Muammar Al-Qaddafi) - the story in the game's manual was deeply altered, Konami's Ultra publishing company took considerable (and rather childish) liberties with the original Japanese source material, where Vermon Cataffy is described as "a once tranquil shepard boy, who grew up on the remote banks of the Sam Sam River in outer Mongolia with his 27 sisters, turned to terrorism at an early age"... What were they thinking ?
[US] "Metal Gear [Model NES-ME-USA]
[EU] "Metal Gear [Model NES-ME-EEC]