Oh, that was when I was arguing that Roy was a boring-ass char in Order of the Stick because he's basically what you get (which he toats is) with Aman arguing against me.
I don't think that really conveys what I meant though - I like evil characters because their motivations, their reactions, their natures - they make far more sense to me than a lot of the heroes. Heroes are usually meant to be pinnacles of human nature, of the greatest things that we can achieve through self-restraint or perseverance. Villains are what usually happen when we give in to our own urges, when we let our desires dominate our actions.
You get a hero (and i'm talking an actual hero, not a D&D type hero who kills for the lootz) then you basically get someone whose life is terrible because he strives to put himself in the worst situations constantly for the good of other people, and when they finally do something for themselves, it's usually something boring and unrewarding that is meant to further show off their virtue.
You get a villain, though?
A villain, a good villain, is forced into their role. They aren't just evil because they like being evil, not at first. They were wronged, always, something terrible happened to them and it affected them somehow. It turned them dark. This is necessary because your villain can't just be a one-dimensional reckless asshole who punches people for kicks because those people (outside of annoying little children) do not exist, and having a villain like that just to make your hero seem nicer is transparent and aggravating as hell.
That villain sinks into their darkness, or they embrace it. They let it take them over, and they do everything they can to fulfill the desire that this darkness has instilled in them. You get villains like Dolarhyde in the Red Dragon, who was abused his entire life by everyone he loved, including the woman he loved the most - his grandmother - for his cleft lip. You see what drives him to kill, what makes him become the Dragon; you see his struggle when he does not wish to fall completely to the Dragon but goes into it at the end because he has nothing else, he is weak without it.
The good villains are good because their strength is their pain, their darkness, their suffering. They wield it like a weapon, hold it like a shield, they embrace it because its all they can do.
That's why I think the evil character personalities, backstories and such are just so much more interesting than any hero's backstory - because i've never heard a hero backstory that I love, but you give me a villain like this, like what I describe above, and i'll take him over your nicest hero any day.
Then we get to the actual practical factors - heroes usually just suck at getting what needs to be done done, villains do what they need to. Virtue makes you do stupid-ass things, the smart villains will be far more efficient and will, if they're well done, make you not want to constantly yell "What the fuck are you doing you challenged child?!" at the screen/page/etc.
Villains, when they accrue great power through their darkness (see: Dracula) can also become among the most absolute badass things ever - because while a powerful hero is nigh-typical, when a villain gets that power through sacrifice of themselves - usually their past selves, their humanity, their goodness (as is usually the case) it gets a result a hero can't ever match, because a hero can never sacrifice what the villain does to not have to be weak - it's what makes the hero the hero.
Anti-heroes are basically just heroes with slightly grayer moral codes to try to tag along onto the far more easy-to-emphasize with, more efficient villain train.
Anyway, that's my view on everything - do with it what you will.