I think one problem with CGI, as technology advances, falls into "Uncanny Valley" hypothesis.
http://en.wikipedia.org/wiki/Uncanny_valley
As you approach realism in animation you reach a point were things seem almost realistic but there are intangible aspects to the scene that lead you to reject what you are witnessing. This is exaggerated when movement and physics become involved. The "valley" is lessened for stationary CGI effects.
