I love the title of this thread. 
I think attractiveness is in the eye of the beholder, a thing of taste and preferences, and everyone has something that makes them attractive, but since you phrased it that way... 
My two main OCs (as most of my OCs) aren't humans and they have a bit different way to think about appearance. Angels and demons are born as adults and born into a social caste of three (per side). Veidja, as battleangel, and N'Arahn, as demonlord of the warmonger caste, are both fighters by nature. Even though both of them can be attracted by very different people, they appreciate strength.
So, even though they don't like each other, they would find each other attractive (if they would think about it that way).
For others they maybe would be a bit too much on the hardened and scarred side. But for them it's just proof of their nature. In my eyes, well, both are handsome. Fit and muscular, with a fighter's elegance. And N'Arahn has this awesome long black hair... 
While Veidja doesn't think much about her appearance, she has a glow around her that makes her stand out when among humans. Those won't really notice the glow, but something that's off and special in a good way. To be clear, that's nothing that's special for Veidja, it's how angels effect humans in general. But since Veidja doesn't dress up or something like that, I think she wouldn't be that striking.
N'Arahn on the other side... He has a lot of confidence and likes it to be admired, at least when it comes to humans. He's about 2m (~6ft7) and he knows he's quite impressive. He can be arrogant, but that's more for playing for him. He just feels very comfortable the way he is.
Not sure how much this answered the question. 
Well, as I said, in my "arrogant opinion" they are very attractive. 
