The average Japanese woman is not beautiful but on average they put far more effort into their appearance. If you are particularly attracted to Japanese women you will find a large percentage of them to your liking but they are by no means on average more attractive. I would say it's likely the other way around. Effort and a good sense of style really does elevate a woman quite high though. If you go to a fashion hub like Shibuya, the average attractiveness of a girl sky rockets as they really put in a LOT of effort to look good and you'll be seeing a stunning girl every minute or so. It's not that more attractive women hang out in Shibuya, it's just that when going to such a place, they put in the maximum effort, they probably spend 2 hours getting ready to go out. Without all that effort they'd probably look bad. Amazingly beautiful girls like actresses and idols are rare and even some famous Japanese women look pretty mediocre or even unattractive without make up yet still look fantastic with the make up and gather huge followings of adoring fans.
TL;DR: On average Japanese women are not attractive but they can make themselves look very good with effort. Without it, they look quite bad usually.
