Virtual Reality is a simulation that has been done in games in different ways. For Metal Gear Solid, there was released a separate disc called Metal Gear Solid: VR Missions, which consists of over 300 VR missions. VR missions can also be found in Metal Gear Solid 2: Substance. These VR missions are basically scenarios with certain requirements and certain conditions. Like go through a level without killing anybody and without being seen. Control a stinger missile through a maze of ductwork and hit the target. These were either on a vector plane or a location. But the guards don't drop and bleed, they dissove like a program.
This was also done in Assassin's Creed. The scientists in the game used a machine that they made called the Animus that took your genetic code and created a simulation of your ancestors in their respected time periods, thus creating the reality in the past.