Gollum always looked fake to me. For the time it was great CGI, but it still looked fake. This is my point when it comes to CGI - it is not real. A plastic mask is real. It may be poorly crafted and look like crap, but it will still look real because it is real and not just data on some computer.

Jabba looked great in ROTJ in 1983, in 2003, and will still look great in 2033. Gollum will be considered a joke in 2033. THIS IS WHY CGI IS BAD FOR FILMS UNTIL THEY HAVE 100% PHOTO-REALISTIC TECHNOLOGY. Filmmakers stop using FX in the proper manner; as slight-of-hand (as another poster put it), and instead put it front and centre where we can see how fake it looks.