the over use of CGI can totally kill the atmosphere a movie sets.The reason CGI is used so much isnt because it's more efficient, but because it is cheaper. When someone actually uses CGI to achieve somthing that they couldnt otherwise, and put forth the effort of going all out, then we get some spectacular results. The best example of this to date would have to be Lord of the rings, Jurrasic park wouldnt have been the same movie if not for CGI, however, Nothing can beat good ol fashion cotumes and animatronics. I think one of the worst examples of CGI in a film is Alien 3 ( i know there are far worse examples) The computer generated alien killed the tangible feel and lagitamcy that the franchise had set in previous films. The fakness of the alien was more than enough to kill the tone of the film, it even overshadowed the terrible script.
I think CGI can be a good thing, if balanced with realism, a total CGI movie, rarely ever works.