I've been trying to answer this question for myself a long time, and... it is bit too hard.
But for a few generalizations (in real life, not artwork):
I like brownish hair, a little read or light brown/blonde is fine. I hate dyes, all dyes, it makes the texture horrible.
I usually like shoulder +- 2 inches, but this can vary a LOT based on the rest of the person's appearance/personality.
I LOVE bangs! Almost all bangs, especially symmetrical ones, or straight across the forehead ones that goths (who I'm not typically into) often have.
I like thin hair, the type northern Caucasians and Orientals usually have.
But honestly, even though hair is probably my most important "looks" category, I can't think of any "ideal" hair style, just a bunch of things I often like. Besides, the whole is more than the sum of the parts, so all of these generalizations may be wrong in a certain instance.
I generally like whatever looks best on the person. But I tend to go for guys with darker colored hair. Or with wacky colored hair. Style also doesn't really matter as long as they look good...but I do have a thing or mohawks.
Yes so I have natural waves, and I love them by the way. I don't really have to do much on my hair just a little combing is good enough. My roommate says that it looks very healthy because it bounces when i walk. But sometimes I straighten thems, and sometimes I curl thems to give it a different look at times.
mine was wavy last time i had it long enough to see....now i have it very short and i bleached it so....its straight and a little messy oh and maybe little nappy if i forget to condition it