What Makes a Character Great

Yesterday I saw X-Men: First Class and I thought it was amazing. The X-Men movies have always been my favorite superhero movies and that doesn't look like it will change anytime soon. I could not help but notice that Charles Xavier and BBC's version of Merlin have a lot in common. As a matter of fact, some of the dialog in the movie could have been in the TV show. Both Merlin and Professor X fight for people who would have them killed. In BBC's Merlin, magic is outlawed but Merlin continues to use it for good and has saved the life of King Uther who would have him killed. Professor X fights for the humans, some of them would side with the mutants, others are afraid and would have them killed. In both the TV show and the movie, there are conversations where a mutant/sorcerer who try to get the hero to join their side, telling them they betrayed their kind, that humans will never except them and view them as a freak. However, both Professor X and Merlin fight against those people. Personally, I find this trait in a character amazing. Three seasons into the show and the character of Merlin has done nothing, not even once to irritate me. There is a very slim number of characters who can claim they have never done anything to bother me and none of those characters have been around for three seasons. Not every time does this type of behavior work though. One of the very few times Willow from Buffy the Vampire Slayer annoyed me was in the episode titled "Pangs." Most of the time I love Willow but not this time. She kept talking about how the Native American who was attacking Sunnydale was wronged by the white settlers and wondered if it was right to kill the Native American. Though I agree with most of what she said (the Native Americans were horribly treated and I do appreciate how the show did not simply overlook that) I did not agree with her obstinence to kill the Native American. The cursed Native American had already brutally killed a number of people and had infected her best friend Xander with every disease the white people had given the Native Americans which would guarantee his death. Despite this, she wanted the cursed man to live. It was not until the group was being shot at by multiple beings that Willow finally gave in. So how come when Merlin and Professor X fight for those who would kill them, like the cursed Native American, it works but for Willow it did not? How come one trait given to a character can be found endearing and another annoying? If I could just unlock the secret then I would already have a novel published. I guess for now I will have to ponder on why Wesley Wyndam-Pryce's betrayal caused my heart to break for him and vault him to my favorite character in Angel while Morgana's betrayal on BBC's Merlin caused me to dislike her? Maybe that's how the writers wished for it to be interpreted by the audience. Still I'd like to know why Luke from Percy Jackson can make my heart melt when he keeps showing signs of belonging to both sides of the war but when Anakin Skywalker keeps changing his mind it gets irritating.