zombie84 said:
Shakespeare spoiled lots of his endings in the first few lines of his plays. That becomes part of the dramatic suspense--you know the ultimate fate of the story, but what you don't know if how things unfold, who does what, and knowing how things turn out gives you new dramatic mechanisms to use. You can use it to mislead and twist the viewer, knowing she or he expects certain things, or you can use their knowledge to play up the drama. A more banal instance of the latter is in horror films where the audience knows a monster is lurking behind a door but a character doesn't--the suspense becomes not "is there a monster behind the door?" but instead, "no, don't open that door!" and then the audience has to squirm in suspense wondering how the character will survive.
Anyway, most blockbuster movies like Star Wars are predictable. Will Luke beat the bad guys? Yes. Will he save the princess? Yes. Will he survive the ordeal? Very probably. But how does he beat the bad guys, what situations does he have to get himself out of, and how does the princess get rescued? This is the suspense structure of Star Wars. That's also one reason why it was downright shocking when Luke got his ass kicked in ESB and all the good guys lost--that's not supposed to happen!!
This is true of 2011. I don't know if this was as true in 1977. Remember, Star Wars was only the second "blockbuster".
Two points in regards to the "does predictability negate tension" argument:
First, I feel that if a movie really draws you in you aren't sitting back and analyzing it. You aren't thinking to yourself; "I know what happens next". Very few films do this. I remember one reviewer saying how he had completely forgotten Han Solo because the space battle at the end was so exciting. Result? When the Falcon swoops down out of the sun to save Luke it is an incredible moment (original audiences were cheering in their seats). Should we, as adults, have guessed that Han would come back? Yes. But did we? No. That is what it means to have made an engrossing experience and a great film.
Second; making a prequel is not the same as making a predictable film. In a prequel we know right down to the specific details the fates of the characters (killed by Darth Vader in a duel on the Death Star to allow Luke and his friends to escape). I'm sorry, but you cannot have any drama if these characters are central to the film.
Conclusion - the prequels main character should have been Luke and Leia's mother, since her fate was the only one that was somewhat in doubt (pre-prequel fandom often debated if she really had died or not).