I’m going to take a bit more of a moderate stance on this one…
Ultimately, I don’t think ANYONE on OUAT is more or less evil or good than anyone else. I think the point is, each and every one of the characters has the ability to be as good or as bad as they so choose. I think it’s important to remember that each character has free will (for the most part, excluding the whole Rumple was Zelena’s slave part) and for the most part, has chosen how to act and react to the life they’ve been dealt. Example – if it were Charming who was called into the Ogre Wars – would he have listened to some crazy gal with her eyes on her hands and purposely injure himself; essentially kicking off Rumple’s storyline and decent? No, he probably wouldn’t. That doesn’t make Charming good and Rumple bad, it’s just that each person would have made their own decision in that matter. If Snow and Regina’s fates were reversed, would Snow have become the Evil Queen? I don’t think she would, no matter how much Rumple tried to get her to give in to her darker side. But, Snow was capable of letting Cora die, and chose to essentially kill Cora.
Yes, their pasts all play a part in it. Snow and Regina are both different, partly because of how they grew up, and same with Rumple, etc. But you can’t be a slave to your past. You can’t blame everything on other people, because ultimately, you are responsible for your own choices. So, I don’t think you can sit down and compare Person A to Person B and say A is more evil. Because they all have the potential for good and they all have the potential for evil.
We all know hope, true love, home are huge themes on OUAT. But I think the concept of choice is also a big focus, though played out less blatantly. Playing the Blame Game is now you get into serious trouble with this show – and I think the writers do that on purpose, go get the viewers to sit and give pause…of course, I think they sometimes underestimate some of their viewers’ passion for the show and their own personal favorites…. 😉