I would want an extremely realistic infinite dynamically-generated open world game that basically combines every game we have into one. You put your VR headset on and you can barely tell the difference between reality and the game. What you imagine is suddenly constructed before you in real time. You can get in a car and cause chaos, escape in a farm meadow by a creek, climb a skyscraper, or start a war. There will be pedestrians in the game that you can talk to about anything you want, and the conversation/accent/amount of people will all be determined by the environment you’ve created in the moment.