A profound question, the-negative.

I'd turn this question around and ask what is it about reality that makes it seem real. When you know that, you know what to do to simulate it. My ideas are in my ebook and too much to repeat entirely here.

It's clear that trying to 're-create reality' is futile. What would be the point? Just use a camera, go see a movie or simply enjoy the real thing. Seems to me the trick is to suggest the essential features of reality (via the best methods of visual grammar, best models, textures, lighting, props, etc.) and let the viewer's mind supply the rest - as usual. Please remember that all we have to work with is a few million tiny glowing colored dots on a 2D surface.

So, it's a kind of high-quality caricature. As in previous media, the artists job is to pick out and express the essences.

Some convincing qualities of reality:

1. Chaos & randomness:
         -Irregularity (except in artifical constructs & artifacts)
2. The 2nd Law of Thermodynamics
          -Wear & tear (e.g. 'rust never sleeps')
          -Evident birth/death/growth/decay
3. Immense diversity
4. Abundant life
5. Multiple levels of detail
6. Complex light effects:
        -Light absorbtion, reflection, refraction, refraction caustics, diffraction, particle scattering, etc.
7. 4 dimensions:
           -3 spatial dimensions + constant change through time (animation)
           -Means simulating depth effects is critical
8. Analog nature, not binary. Continuity and smooth transition from one micro-environment to the next in any scene. Sines, exponentials and such smooth functions are everywhere. Abrupt transitions are rare. No visible descrete steps or quanta (until you get to subatomic dimensions)
9. Gravity effects everywhere (in scenes on planetary surfaces and most air vehicles)
10. Defects & affects of human visual perception (simulating these helps with realism):
          -Depth of focus
          -Motion blur
          -Focal lengths
          -Visual dynamic range
          -Eyeball neural network and brain 'fingerprints'
              *Sensitivity to symmetry
              *Sensitvity to image edges and corners (in cropping and composition)
              *Optical illusion stuff
              *Color scheme effects     

...my 2 cents   :o)