Darkness or Light? Philosophy in Knights of the Old Republic.

Let's put it this way: in every universe (and I don't mean outer space...), there is good and there is evil. In Star Wars, the Sith, to a greater or lesser extent, represent evil, just as the Jedi represent good. What makes the Sith better than the Jedi? They live serving themselves, they do what they want, they don't obey an order or a code like the Jedi do. In general, if there is no evil, then there will be no one to oppose it.