And remember when Greg’s boss was killed? How did he show up alive later in the movie? Because the system was rebooted. Because it was a simulation. The very fact that Greg and Isabel could control people and move objects only on one side demonstrates which world world was real and which was not.
When Greg and Isabel were back to their real home, they possessed no powers at all. They couldn’t control people. Anything “miraculous” was through science, through technology. The producers clearly drew a line where one side had fantasy and the other science and reality.
Those who make the case that this is about drug addiction also say that the “real world” is Greg’s escape from his troubles. However, Greg was miserable in this utopian land of plenty. His wife was having an affair and even small things like the pool water temperature made him upset. He had achieved greater happiness in the simulation where he was unemployed and homeless.
Bolstering my case that the utopian world was the “real” world is that the creators made a point to show that people were philosophizing that they were actually living in hell. So much for this being a drug-addled fantasy. Greg’s escape from hell is going to a world where people think that they’re in Hell?
Considering the fact that reality was only able to be manipulated in the simulation and Greg was unhappy in the real world, I don’t see how any one could think that this movie was about drug addiction. Unless they were on drugs when they watched the movie.