Real textures, or rather pictures (Textures with little depth, transparency, and has angled, pre-existing lighting and shading.) placed in the game like this can make the game look real in certain places, but it only seems to work well on relatively flat surfaces (Which, in turn, makes the reflections look realistic on the car.), and tends to highlight other issues with the graphics. It almost looks like a real picture was pasted onto the background.
As soon as you introduce somewhat complex geometry, animation and other graphical effects, it tends to fall apart. I think one of the main reasons why it worked so well with GTA IV is because of the simplistic geometry of the city, or specifically, the buildings.
First time stumbling into this thread, and I'm in awe. Viewing these on my phone earlier, I actually had to do a double take as some were just too good to be video game screenshots.
Wow. Just wow. Excellent work guys/gals.
(and to Rockstar* for nailing that lighting)
Mine are nothing special, but I thought I'd share the few that I've taken when messing around in the PS4 version so far. All are taken from the social club website, so forgive the resolution.