TheBoost said:

I'm confused at your objection that it was pushed as THE storyline. Isn't all EU "THE' storyline either between, after, or before the real stories of the movie?

Shadows was made a special fuss of, treated as more than just ordinary EU.

I don't see how Xixor is a 'Mary Sue.' He's the villain, does villainous things to forward the plot, is clearly and repeatedly thwarted by the heroes and then pwned by the other villains.

Xizor is a Mary Sue because the story goes "Look at our cool villain, look he's so cool he can rival Darth Vader and get fresh with Leia."