This system would require direct connection to signals from your brain, intercepting and consuming them, never reaching your muscles. Resting comfortably with REM-like paralysis, you control your game character naturally and intuitively, moving it and not yourself, all from the comfort of your couch.
Technology like this already exists in its infancy, such as providing moveable arms and hands to those who have lost them:
"Move Arm" ---> Engage Robotics ---> "See Arm Move"
"Move Arm" ---> Animate Game ---> "Feel Arm Move"
When will this technology be available? What bottlenecks need to be overcome for it to exist? How much will it cost? What other applications could it have? Will it be released before Episode 3? ;)
And this is not to mention the cognitive trouble this could lead to. Isn't hard to imagine a situation such as Mal from Inception happening.