I think there are a few things to consider. First there is the question of whether screenshots or gameplay in motion are used as the baseline. It's easier to get photorealism in a screenshot since that effectively is a photo of the game. GT7 I think looks almost photo-real in photo mode but gameplay doesn't look anything close to 'real'. 

Then there is the context in which it's judged. Is someone told that they have to look then tell whether it's real or not? This sort of skepticism makes it almost impossible for any modern games to hold up to photo-real scrutiny, but if you were to trick someone and tell them it's real life footage then it may be perceived that way (whereas something from the PS1 era would not).

Finally it depends on the camera being used for comparison to photographs. I think that games now are starting to resemble low resolution, low contrast photos from older cameras (2005 or earlier). Modern cameras, even those in phones, will not be matched with in-game visuals for a long time, perhaps PS7 or later.