Most Helpful Guy
Depends on the girl, her character and her face. Some girls look better with short hair, usually if they have quite angular features or high cheekbones for example, as it accentuates it - and long hair suits an oval face by framing it.
I wouldn't generally like REALLY long hair - it would seem to me a bit immature - like something little girls do to pretend they're a Disney princess or something like that; or just unkempt like they didn't take good care of themselves.
It really does depend on the person. It takes all sorts to make a world! It would be very boring if everyone had the same haircut because they thought guys thought it attractive!