During the Boot Camp 2014 press event there was a wide range of Metal Gear memorabilia on display, including an MSX2 system with the very first Metal Gear running on it. Kojima explained on his Twitter that he always had an image in his head of what Ground Zeroes is today, even back than, but due to hardware restrictions it wasn’t possible to make this a reality, until now.
2D dot pic w/ no scroll screen. No blind spot. Snake was able to ride the track but not to drive. Not able to CQC or crawling, or even had not voice, but the image of GZ today precisely existed in my mind. Things existed in MG. Elevator, duct, carbon box, warning mode, danger mode, close combat (punch), 2 way (CALL+SEND) radio, & enemy’s view. Things added in MG2. Crawling, soliton radar, evasion mode, sounds mode, carbon box for transportation, and “Look at the BOB” trick, etc.
Kojima said before that with Ground Zeroes he was finally able to create a game capturing the tension of The Great Escape, a movie that inspired him to design Metal Gear in the first place.
Source: Hideo Kojima Twitter