It's difficult to formalize what "realistic CGI" or even "CGI" means. Most of us probably have a loose definition that's something like "the rendered output of 3D models that looks like something familiar in the real world," but that's insufficient. One could take 100 bitmap frames of video from a camcorder, then use a computer to generate 100 identical or nearly identical bitmap frames. This would be realistic by de…
To me, the tools are getting so good (GI, HDRI lighting, MoCap) that 'seamless/not seamless' is soon going to be the only judging criteria. Of course along with visual aesthetic which will always occur in film whether you're using a physical camera or virtual.