I am not a good artist and neither a good designer. However from a ‘real’ audience point of view, I know honestly what I like and it is not something that what others told me to like or what to hate. If I were to design my own anime characters I’d follow these design principle:
“Design and decoration must seduce, shape, and more importantly, evoke an emotional response.”
That’s it, it must be able to ‘seduce’, something lovely to the eyes, pleasing to look at. Anything that’s opposite to this would be deemed as ugly. How do I measure it? Well for me if the look alone is enough to seduce without the help of the plot/story to support it then it’s won already. I’d take keion for example, where there are cases where people fall in love with the characters even without/before watching the anime. Miku Hatsune, the Vocaloid doesn’t even have a fixed personality to begin with, other than being a 16 year-old girl as touted by the developer/creator, still managed to become a world-class “pop star”. Her derivative, known as Black Rock Shooter is also doing very well. Not to mention the female characters from the bullet-hell shooting game Touhou Project (all of them) also have thousands of fans worldwide. If you ask me to show the example of “ugly” character then I have not much to say as I normally don’t watch/follow what I hate. After all isn’t that what fans have always told the ‘haters’? I mean the popular saying “If you don’t like it, don’t watch!” However stumbling upon hateable stuff in inevitable or impossible. That said, I hate the design of Panty & Stocking (the anime). In fact I think most people like it because it has the anime to support the design. I don’t think the some people who love it now would love it if it was from some American cartoon that carries different name/title and different story.
Of course design alone is not enough if we’re talking about anime in general. That’s why I always insist that anime has to have proper plot/storyline to accompany the characters. After all characters are designed for the sake of the plot, not the other way round, where you could design a character to look like in any way you wanted it to be solely based on the plot given to you but there’s no way telling what kind of plot from a character design alone. This is what I meant by “emotional response”. For me the genuine emotional response can only be triggered by the story. It doesn’t matter how bad the drawing is. It also doesn’t matter how bad the animation is. If it is enough to evoke an emotional response in you than it already won half of the battle. I maybe biased in this and I could be wrong too but again the one who is being entertained here is me and this is why how the character look and in what story they’re in is important to me. Otherwise I would not find them that entertaining. For any anime to entertain me, it has to do the above without fail. With that said, I do admit that my No. 1 favorite character, Mami-san (and the rest of Madoka Magica characters) is badly drawn and I even criticized it in my post here. Also I never liked SHAFT anime studio to begin with but the story and my emotional response towards it saved Madoka Magica from being dropped/hated in my watchlist. Yes I am extremely picky but regardless how picky I am it doesn’t concern anybody.