I tried as Japan once and sought to remain uninvolved and work maintain good relations with the US and UK, while researching advanced technologies. However, the HOI 2 game design nevel lets you take a "bad guy" and turn them completely into a "Good Guy". In ended up in a war with the US anyway and quit the game.
In general I like to play minor sideline nations. I've been Argentina, Mexico and Sweden, and as Mexico I did get to have a brief fling at greatness after the USA entered "WW2" and most of its forces went overseas. I invaded the SW US and got as far as Oklahoma. I quit after the first US counteroffensive made it clear I would soon be toast.