I just think some of the not so bad ones (But their face is like too long or something) if they just made some of them younger. like in their 20's early 30's then they probably wouldn't look as bad.
This is due to the hyperrealistic art style. The faces are exaggerated in some (or most, or all) of their attributes.
Hence why some of you might find most of them ugly. Because there is literally no perfect face. And if you exaggerate aspects of a face, it will always look contrary to the common sense of beauty.
By the way - I like the faces very much. But I usually go for that extreme look as well.
By the way 2 - I heard from a lot of people they liked http://mnfu.files.wordpress.com/2008/07/the-joker.jpg as the Joker, but not http://4.bp.blogspot.com/_uLEl_Km4s5c/TJy4ci9ITnI/AAAAAAAAALg/md-HtwuAwB8/s1600/The+Joker.jpg, which has this extreme facial attributes. (Those images are great, btw. A similar pose, a similar facial expression, but a completely different style.)