We won't have photorealistic game for a long time because how way our GPU and 3D graphics works. With a pipeline architecture, every single object inside a game is rendered individually. Things like shadows and reflections in games are all "gimmicks" or "Tricks" to make it seem like shadows and reflections. Until our computational power increase to a point where we can do massive ray tracing in real time, we won't have a truly photorealistic games.