Not always, not every time, but sometimes, Japanese food is simply the best stuff there is. Saying that, I have to admit that there are some things I strongly dislike about the food in Japan. My wife will barely bear me to say it, but I simply do not comprehend why the single flavor in half the dishes is salt. Udon, Soba, Ramen, and many of the fish dishes tend to be dominated entirely with salt, or to be rather bland, or worst, bland and salted.
With that aside, the sushi, when it's good, is simply one of those foods for which there can be no equal, no matter how many foods are as good. That said, I will admit that I did not feel, after Japan, that I could not have sushi anywhere else. I still believe I will easily be able to eat sushi in American sushi shops - in fact, I still hold that the best sushi I have ever had was a piece of Tuna sashimi in Seattle. That said, in Japan or Stateside, it is an incomparable food.
For those who prefer to eat well on a tight budget, Japan, expensive as it is, is one of the best places to do it. The Oyaki, dumplings stuffed with vegetables, are far more savory and filling than they sound. For 120 yen (about $1.50, at any Konbini or Oyaki shop (of which there were no shortage in Nagano) one can buy a portable snack, and two or three will fill the modest appetite.
When the modest appetite is lost to the strong appetite, I have rarely found a match for Ramen. For about $6, one can get a big, steaming bowl of ramen in a pork or miso-based soup thick enough that even with an empty stomach, you'll be struggling to see the bottom of your bowl. Sadly, again, the best Japanese food I have had was in the United States - my favorite Ramen being at Daikokoukuya (sp?) Ramen in Los Angeles. I suppose I just didn't manage to find the unhealthy, greasy-spoon places where the really good Ramen is in Japan, but at Daikokukuya, you get a big bowl of rich and steaming pork-back broth, simmered for days, with plenty of toppings - a hardboiled egg, pork slices, and bamboo shoots.
Great, now my mouth is watering.