"My backstory is the coolest thing about this whole series. Suck on that, Bella Yawn."
Everybody in the world... well, every non-fan who watched the movie version of Eclipse had the same reaction: Why wasn't this movie about a hot blonde chick as a killer vampire bride inflicting horrible revenge on the men who gang-raped and beat her to death? Why were we instead watching an ass-numbingly dull teen melodrama about two supernaturals wanting to bone a lipless durr-faced girl?
I am serious - a lot of people who hated Eclipse and the series in general were deeply baffled by the fact that for some reason, we were getting Bella's story instead of a bloody Kill Bill vampire movie involving a vengeful Rosalie in a 1920s bride dress. "Why?" they asked. "Why aren't we getting a movie about that? That is AWESOME. That concept kicks ass. It would make an awesome movie! Why? Why, Lord God?"
Easy answer: because the entire Twilight series is basically Stephenie Meyer masturbating on her computer.
- Including an awesome kickass plot means that it might focus on someone other than Bawla.
- Because Rosalie is gorgeous, blonde and attractive, meaning that we're not supposed to like her.
- Because Bella, being Smeyer's Sue, is the center of the Twilightverse.
- Women are not supposed to do stuff like Rosalie did. They are supposed to sit there and flutter with fear while their boyfriends do stuff.
Sigh. Having explained that, The Rosalie Cullen Syndrome is basically the name I came up for characters and backstories who are infinitely awesomer and more interesting than the actual main characters and plot. This seems to happen a lot in bad fiction - you'll have a character who has some awesome backstory or hints at something dramatic, but it's shoved to the side because the author wants to focus on their dumbass Sues and boring plots.
Obviously, Stephenie Meyer is guilty of this in a BIG way. We're treated to endless whining, wangsting and minutiae about Bella's life, instead of the Civil War vampire army that Jasper was part of, or the whole Rosalie-as-killer-bride thing. But Laurell K. Hamilton is also a repeat offender, since EVERY character in her universe either has more potential or is more interesting than her Sue. Amelia Atwater-Rhodes does it too. Dennis L. McKiernan does it a little too, although not nearly as much as these others.
So in conclusion, if you're going to give a character a kickass or interesting backstory, don't make your main story incredibly boring and your main characters even duller. It will just highlight that you COULD do better.... but you're choosing not to.