I can't think of any earlier than MK that used photorealism and actually had playability! There was stuff around in the mid-80s (Arcade machines rather than available on home consoles) that had photorealism but were obviously just focussed on the graphics and had awful gameplay and pretty much zero responsiveness.

I even remember playing some sort of fantasy adventure one from mid-80s that was 3D and photorealistic, it was one a table with a convex bowl with projectors for holograms. So you had photorealistic sprites that were actually walking on top of the table. But when you hit a button or moved the joystick the lag before anything happened meant you were already dead. Cool to play once just to see and think "Wow this is the future" but zero fun.

I had a quick google to see if I could find a name or date to support my vague memories, couldn't find the one I was looking for, but this article has a few early photorealistic stuff: http://allincolorforaquarter.blogspot.com/2014/03/hologram-time-traveler-revolution-that.html

Also seeing the mounted gun games in the article reminded me they were photorealistic very early. Some were film quality, basically an actual film of a wild west scene with cowboys popping up you had to shoot (I'd the gun was a light sensor sensitive to specific wavelengths and could detect whether it was pointed at a cowboy or just background when the trigger was pulled?)

But I can't think of anything for home computers or consoles that predate MK, and I remember MK had a lot of hype based on this when it came out (There was even stuff on TV about the making of it, showing how they'd captured videos against green screen of the actors performing the moves etc.) so assume it could well be the first home system one.