[Nyororin]

There are two big reasons for this - improvement of the games (updates) and adjustments for markets.

I think that you`re talking about games that are not originally Japanese being released in Japan - correct me if I`m wrong. The other way around is a bit different.

First, improvement. Bugs will be patched, and the developers have a chance to add in some new features that maybe they didn`t have time to put in when the games were first released. Or perhaps they listened to the voices of fans where the game was originally released and decided to add the features everyone wanted. Sometimes, they just think of something interesting to add after the fact.

The Japanese market also has different expectations from games - Developers expect different features to have more weight with fans in different countries. A game will be tweaked a bit toward the market it is being sold in.

I would say most of it is really improvement though. Let`s say that some game maker decides to release a new version of the game that is already out in your country, with the newly added features. How many people would really buy a new copy? The version to come out the latest almost always has the most new features and fixed problems. When it`s a case of being released all over the world at the same date, they`re usually the same.