Sasuke because this entire manga has been centered about him and his descent to evil, even though he turned good now. It would be a better masterpiece if Sasuke continue to be evil.
No worries. OT: Kishimoto really did his homework in Jiraiya's creation and even incorporated elements of the Kabuki playwright Kawatake Mokuami (wrote the Kabuki version of Jiraiya Goketsu Monogatari) into the character.
Naruto and Itachi seem to have the most depth. They are also the most empathatic. When it comes to ethical and moral decisions they are both lightyears ahead of their age group too.