Most Helpful Guy
No general standard for me.
That said, it's rare for me to see a girl with short hair as appealing. Often she needs to have very elegant features like a long neck, narrow face, big eyes, something like this. Those girls often look nice with any hairstyle.
For most women, I think they look better if their hair frames their face, with something like near shoulder length. After that it no longer makes a difference to me, it's all about how the hair frames the face with the way I find women's faces appealing.1
Most Helpful Girl
I'm pretty sure most men prefer long hair.1