Sasuke is one of the most dynamic and well written characters in the series, rivaling only Shikamaru and Naruto. Sasuke will not betray the village again. He is simply becoming a Danzo character, dark but loyal to the Leaf, and Naruto will save him from his inner darkness. So Sasuke can have a happy ending.
There should have been a moment where Naruto became a dark character but got over it. I find completely unbelievalbe that any character can be completely loyal to a village that treated him so poorly during his childhood. Someone should have to pay for that at Naruto's hands.
Itachi is a sociopath. Despite being loyal to the village, whereas sasuke was not, Itachi is much more evil than Sasuke was even durring the Five Kage Arc.
Obito is horrible villain and might be pedophile.
The Sage will not return because if he did then that would be a deus ex machina.
Diedara isn't that great of character.
Lee is also not a great character.
The Uchiha Clan Massacre was unnecessary and completely wrong. When negotations fail, you do not simply kill them all. That is a genocide and a crime against humanity. The leaders should have been arrested and been presecuted in a fair and open court trials.
Anko should have been developing more. For example, she should have been the caption of Team 7 during the Sasuke and Sai Arc.
Sai is a boring and forgetable character.