I think it's all suggestive and depends on point of view. Objectively, technically you can't call anything good or evil, because the terms are in and of themselves suggestive.
Now, here's my point of view. Completely OOC, of course, and based not on their ideology necessarily, but on their actions:
What became the Sith began with the Force Hounds of the Rakata Infinite Empire. They were, for all intents and purposes, the equivalent of Jannisaries, and were merely military personnel. From that standpoint, no, they weren't evil, they were just doing what they were trained to do. After that, it came to a minor schism between two rivaling schools of thought. Again, not good or evil, just different.
This is where we get to a gray area, with the first large-scale schism and the Legions of Lettow. the Legions of Lettow were initially peaceful, supposedly, and just wanted to create a new ideology that was less restrictive than that of the Jedi. The Jedi at the time weren't exactly tolerant of this, and so they spun a lie to paint the Legions as a threat to the galaxy. In a sense, the Jedi were the evil ones here.
Now, as time passed, we had the Hundred-Year Darkness and the second schism that led to an exile that created what we now call the Sith Order.
Now, the Sith's actions definitely make them evil, but the Jedi were far from the heroes that they would think themselves to be. It's arguable that they're even worse because they do all of this while still claiming to hold a sort of moral high ground (the almost complete erradication of the Sith species wit help from the Republic, as well as their actions in multiple wars, come to mind). Of course, this argument more or less fails to hold water when one sees what the Sith became and eventually did (intentionally blowing up a couple of populated planets comes to mind).
In conclusion, the Sith are definitely evil, but the Jedi are far from moral paragons themselves.
Now, based on IDEOLOGY, on the most fundamental level...well...it's largely up to perspective, but I would say that they aren't evil. Cynical, perhaps, but not necessarily evil; although at times it certainly implies evil, but there's been many Sith that drew the line between what they viewed as necessary evil (aka Lawful Evil) and evil for the sake of evil (aka Chaotic Evil). Me, I tend to play Armyss as something between Lawful and Neutral Evil.
Oh goodness...
