But I think I have an answer as to why to new trilogy, despite it's enhanced special effects, did not have the impact that the '77-'83 trilogy had. Simply put, we all knew what was going to happen. We all knew Anakin was going to become Darth Vader. We knew that scores of Jedi were going to be killed off. We knew that Anakin was going to sire Luke and Leia. We knew that Kenobi and Anakin were going to duke it out. We knew Yoda was an uber Jedi-master....you get my drift. There were really no "surprises" in the new trilogy. There were just a few things that made us go "hey, that was kinda cool." But nothing really grabbed you and made you think.
I personally don't think it's that. I think it's because Lucas wanted to make a CGI spectacle, rather than a character-driven trilogy. The only character development there was in the new trilogy was the Anakin - Padme relationship, and that ended up being played out like a high school drama, in part because Hayden Christensen isn't that great of an actor, and because neither he nor Natalie Portman had much to work with in terms of dialogue written for them.
So the trilogy not only ended up being somewhat predictable, but it ended up being good only for the cool CGI and flashy battles.
I wish Battlestar Galactica was re-done before Lucas did the new trilogy, because the new BSG shows that just because it's a sci-fi story doesn't mean it can't be character-driven. BSG's CGI is pretty amazing, but the show succeeds so well because it does not rely on it. If the new Star Wars trilogy did the same, it would've been a much bigger hit, I think.
The only new movie I go back to watch again is Revenge of the Sith, because despite it still being all about the CGI, it still manages (somehow) to trigger some emotion in the end - from Order 66 to Yoda failing to win against Palpatine. But when I finish watching the first two, my reaction is just "Hey, the effects were pretty cool" 