Have to disagree about the new Aeon at Whampoa. I used to live in that area and, having lived in Japan, loved how it was exactly like a supermarket in Japan. I instinctively knew where things were and they had all the things you need for Japanese cooking. Recently went back and since its remodelling, the selection of Japanese stuff has shrunk, while the selection of instant noodles and the same crappy mainland fresh produce you can get at any welcome or parknshop has increased. Just another crappy local supermarket but with a. Japanese brand for added prestige. Definitely not worth a trip for anyone homesick for Japan.
That said, I loved living in Hung Hom / Whampoa, and there's a sizeable Japanese community there.