Let's be honest, everyone complaining about this is really just annoyed that they now have cravings for some McD's.
E: I've never been to Japan, and I'm sure it's still not good for you, but I'm fairly certain advertising McDonalds to Japanese kids and family is a lot different than it would be if America were to do so. What with our ridiculously oversized portions, and much cheaper prices (isn't it like $4 for a burger over there?).
Okay after typing that out, the portion size is the biggest thing, actually. A large fries to go with a burger isn't rare at all in the States, but I've seen pictures of Japan's fry portions and they're waaaay smaller. And considering fries are more unhealthy than the burgers/chicken, that's a good thing.
I tried my hardest to make this not come across as an "I'm an expert" post, hopefully it didn't. Just saying again that I don't actually live in or research Japan, I'm just going off of what I've seen on the Net over the years.