I was watching Avatar on TV earlier and couldn't help thinking that as nice as it is, the CGI really looks fake a lot of times and I don't know what they did on Godzilla but he and the MUTOs are the most alive looking CGI creatures I've ever seen, even their movements don't feel like they're doing things that could only happen through cgi.
Funnily enough I just read an excerpt of an interview James Cameron did a little while ago where he said that you HAVE to watch movies with CG characters in them in 3D in order for them to look real or 2D animations next to humans that exist in 3 dimensions will always look fake. That's funny since I never heard any director complain about that for characters like Davey Jones or Kong. But suddenly people start noticing that the Na'vi aren't that perfect and Cameron rushes to blame it on 2D presentations of the movie.