but by the same token, they didn't leave the theatre knowing that almost everything was fake.
yes they did--again, they didn't leave the theater going "oh MAN. that spaceship was cool!" They knew it was ALL fake. They just liked it. now, it's just a different style of fake.
One of the bigger problems with CGI is that everyone wants to show off that they're using it in behind the scenes stuff, promotional docs, all that. The tool is getting as much publicity as the movie is. That didn't necessarily happen back in the 80's--the studio wasn't trying to show off all their toys all that much. They were maxing out old tech and old methodology, not innovating new ones. Once you start re-inventing the wheel as far as effects go, people realized you could appeal to the "Bang for the buck" style of hucksterism and make the effects used part of the marketing. "We made this with a COMPUTER!! BUY A TICKET!!" I guarantee you that if an effects movie was released that didn't go into detail about HOW they made the effects, people would stop being so nitpicky about em. but in todays moviegoing climate, there's no way that happens. you have to have the behind-the-scenes video blogs and the special on the dvd and the hook in the movie magazines.
Which wouldn't be so bad if it wasn't so much overkill, to the point where you effectively TRAINED the audience to become EXPERT effects spotters. the movie is almost secondary at this point, because people are so used to being the reviewer in their little circle of friends, film has become so democratized that everyone really DOES believe they can do better, that people are waiting to find a seam and log it away. And yeah, there were people who did that in the 80's, too, but they were fewer, and largely marginalized, because people didn't really care. Now that the entertainment industry puts as large a premium on the "Behind the scenes" as they do the movies themselves (check out DVD culture) you have a lot more wizened, savvy and unforgiving viewers with their own skew and prejudices regarding the technical aspects of a movie.
It's not so much that CG is bad (largely, most people can't even tell the difference. they think they can, but they usually screw up along the way) but that it's put itself out there as the scapegoat for grumpy nostalgia due to aggressively marketing itself as something more than a simple tool in the toolbox.