...brain is a strange animal - mine in particular, I think... you are right, grain is just "organic noise"; it changes from a frame to another, and maybe this is the secret of the perception of increased detail (that obviously is not really there); indeed, if you try to apply a static grain, the result is really bad!
@kk650: you order, I obey! (^^,)
Here you are the 35mm grain plate applied over the same screenshot you used before:
http://screenshotcomparison.com/comparison/66357
as you can see, it's more "aggressive" then yours; don't know if it's better or not, but I think it should be seen in motion to understand it.