According to a preview of a near-finished build in the latest print edition of Game Informer Magazine, Metal Gear Solid: Ground Zeroes' campaign can be completed in two hours.
As reported by Kotaku, Game Informer finished the main mission in the prequel to Metal Gear Solid V: Phantom Pain in "less than two hours," although it's important to note this did not include side-quests or extra modes.
Lol, what??? If it's indeed true I'm not going to buy it unless it's sold at a very reasonable price. Who would want to pay full price for a game that's only two hours long??? $30 is still a little steep for that amount of game time. However, in its defense, this does not include side missions and extras.