Japanese developers need to get their shit together. By the time TLG is released Naughty Dog will have produced 3 uncharted games, they even found the time to throw in multiplayer not to mention the fact that they created one of the most impressive engines you'll find from scratch.
Same goes for polyphony digital, square-enix and others. Duke Nukem is a different issue, there where all kinds of external problems, the game even got to the point of being cancelled. The developers I mentioned had all the resources they needed right from the start, it's really hard to justify these 6 year development cycles with anything other than poor management.
Let's put it this way, if every developer took this long to create a game this industry would be in trouble. There are a lot of european and american studios showing us every day that it's possible to create a fantastic game in 2 or 3 years.
The higher ups at SE seem to have realized this since they announced plans to release a AAA title every 2 years, let's see if they manage to deliver XIII-2 this year and Versus in 2012 like they promised.