Eh, I lived in Japan for 2 years, and I don't rate the curry there that highly. You can find good curry, sure, and I have my favourite places, but the baseline isn't that high. People forget Japan has basically been in a recession or depression for literally 30 years. When I think of mainstream food there, what I usually think of is "made down to a price".

I'm gonna stake a claim and say that if you go and buy a pack of golden curry medium, cut up a decent bit of rump steak, add a couple of carrots, potatoes and onions, boil the shit out of all that then mix in the curry, serve on fresh cooked rice with a handful of shredded cheddar - you're having a pretty damn good curry which will be hard to beat no matter where you go.

I'll also go out on a limb and claim that the baseline Japanese cuisine in cities with a decent size diaspora - think LA, Sydney, Bangkok - is better than in Tokyo. You have enough locals to support a lot of restaurants, and they enforce an authentic taste because they know what it should taste like, and they have more money. Your average plate will cost more, but everything in it, and the final result, is better quality.