Originally Posted by
Biff Pow!
Technology advances step by step. Yeah, the movie industry is a big contributor to that advancement, but no single project can go from Tron to Spider-Man. Each project would learn a little more, through "Money For Nothing", The Abyss, Pixar, etc. James Cameron wanted to make Avatar in the 90s, but technology hadn't advanced enough for him to make the film he envisioned. He was part of the advancing that made Avatar possible, but he did still wait for technology to "catch up".
EDIT: More accurately- CGI effects are limited by the memory and processing power of the current computer industry.