Let me break it to you how it is.
1) The best companies back in the NES/SNES days were all Japanese because a large majority of good western studios were focused on the PC, not console. Bullfrog, Westwood, Bethesda, Bioware, Valve, Epic, id Software, and so many more were completely focused on the PC in the early years, so if you only gamed on a console, it seemed like Western developers couldn't put out a good game.
2) We are seeing more of the top-tier Western developers finally move to consoles.
3) Japanese developers seem to be in this rut of only releasing sequels. I know many of you will point to the endless Madden sequels, but for every No More Heroes that gets released we get a Dead Space or a Mass Effect or a Portal or a Mirror's Edge. Now, there isn't anything wrong with sequals, but when you get Capcom, Nintendo, and Squenix pretty much shooting out as many Megaman and Final Fantasy offshoots as they possibly can, it gets pretty annoying.
4) Japan isn't the mecha of video games anymore. It was for a brief time, but now the closest place to a mecha for video games is back in the USA. Even then, we are seeing tons of countries all over the world step up their video game production, particularly in Western Europe.
Japan does still release great games and they are second only to the USA in terms of producing those great games, but their influence has certainly faded.