During the panel at PAX, Kojima answered some questions regarding the Metal Gear franchise, how it came to be, and what the future may hold.
The codename ‘Snake’ was chosen because it was most fitting for a character who is sneaking and staying out of sight. Kojima came up with the character of Ocelot because he really likes spaghetti westerns.
One of the main themes of the series is surpassing your predecessors. That’s why Kojima wanted to put a lot of detail in the character of Big Boss when creating MGS3. He made Raiden the protagonist in MGS2 so we could see Snake from his perspective. Raiden also has to surpass Snake, who is already legendary in the players’ eyes. For MGS4, it was kind of the other way around, players saw Raiden through Snake’s eyes and thought he was cool, they wanted to play as him.
There are still limitations when it comes to creating games, that’s what keeps driving Kojima to create new things. He thinks it’s going to keep evolving and growing, and get better and better.
Kojima would really love to make a game with The Boss as a main character. But that would not be a spin-off, Kojima would make that as a main part of the series.
Source: Hideo Kojima Introspective at GameSpot.