The Pok?mon phenomenon started when two mysterious new games were released in Japan. They were named Pok?mon Red, and Pok?mon Green. Yes, Green. Shortly after, Pok?mon Blue was released. It contained much better graphics than Red and Green. Nintendo of America saw this, and decided that Pok?mon would be a good franchise to start on. They did so, and thus, Pok?mon became a huge hit in America with the first two games, Pok?mon Red and Pok?mon Blue.
Yes, Blue. Here's the tricky part. NoA ripped the graphics from the Japanese Blue and stuck them in Red and Green. Then, for some reason, NoA renamed "Green" to "Blue". So, while Red and Blue were the first two games in our market, it was Red and Green in Japan.
Hence FireRed and LeafGreen. To public knowledge, Nintendo of Japan had planned on releasing the two Pok?mon games on the Gameboy Advance. The reason for this is quite unclear. But as far as we know, NoJ has no intention of creating further remakes. This may change in the future, but we'll have to wait and see for now, I guess. o_O