Well my SW is fairly limited (I saw all the movies, the Clone Wars shorts and played through KotOR), but in my opinion the Sith are evil, since a major part of their philosophy is lust for endless power...
I wish the Jedi didn't distanced themselves from emotions that are good in nature (love etc.), but it works since Jedi are (very) basically a cross between Buddhist monks and samurais.
btw, is there an EW comic about Sith remorse? that would be pretty interesting