The Sith are not naturally inclined towards evil. The Sith way is the way of peace.
Consider Darth Vectivus (I believe that was his name). Ever heard of him? No? That's because he wasn't a power-hungry egomaniac out for power over the galaxy or trying to wipe out the Jedi. He did no evil. He just existed, learned. Died of old age, surrounded by family and friends.
(That is all very well explained in the book "Betrayal", book #1 in the Legacy of the Force series)
That is why the Sith should rule. Palpatine was simply power-hunrgy, and that was his entire problem. Anakin Skywalker was afraid of losing his one true love, Padme, and that is what brought him down. The Sith view love as something to embrace - and be able to sacrifice. Anakin completely and utterly failed to learn this lesson, and he paid the price for it.
Don't get me wrong, I like the Jedi, but the Sith seem to have the right idea.