You really think Lelouch is as evil as Iago? Moral dilemmas in Geass are more complicated than that. Suzaku was betrayed by Lelouch, certainly, but he's betrayed practically everyone that it's possible to betray, himself.
And Lelouch's goal, at least, is noble. The Elevens are worse than slaves, they are captives in their own nation unless they apply to be 'honorary Britannians'. Slaves are at very least protected by their masters and valued as property. The war existed before he became Zero, as did the Japanese Liberation Front. A lot of those people were going to die anyways. All he did was try to give their deaths meaning.
By crushing an evil, racist, oppressive, and generally disagreeable empire. Since when is that not a noble goal? Even if it's for less-than-savory reasons. I have to say that in this case, the ends justify the means.