I was just about to say it's a shame Ventress wasn't in the movies, she could have fit in well into the prequels.I was about to complain about the fact that the person who gave Anakin his scar does so offscreen in the movies and is never even mentioned outside of the EU and didn't even get proper character development until the Clone Wars by Dave Filoni.
And if Grievous wasn't made out to be a joke of a character I think he would have been great for all three movies.