Everything you need to know:
There used to be an old axiom around Hollywood that went something like "there's only three scripts in Hollywood and a hundred thousand rewrites." Truer than it should be.
Just like the music biz, no one wants to take chances on something off the beaten track; they try to make it a science. Rework the formula, sign a proven star, toss in some CGI, market it aggressively, break even on the box office, make your money in DVD sales.
Tron's "plot" was corny the first time around--it did break some visual ground with CGI, though, back in the day when optical FX were the norm.
I think you could make a pretty good case for Avatar being a rewrite of Tron, but with a bigger budget.