Before i write this, let me just say i own the American version of Pokemon Diamond, and by the time this comes out here, it would of been out for a few months, give or take
Well, first of all Pokemon Diamond/Pearl is based off the Anime counterpart in Japan, you journey using either a girl or a boy character, the girl goes by the name of Hikari, which means Dawn in English.
Also, this game has sold Millions, and i mean Millions in Japan alone, and has taken America by storm too!
Before saying anything else, just be careful because Pokemon Diamond or Pearl has game specific Pokemon so you may not be able to catch a pokemon you like because it wont be in the game, the only solution to this is to either trade with a friend with Pearl or Go Online..
The Game is Based in the land of Sinnoh, its a new Region
Without Spoiling, the game has a whole bunch of new features, like, well use of two screens for the journey, a clock feature, online, friend codes, trading, once you beat the elite four you can transfer Pokemon from the old Gameboy Advance games, but you have a limit of 6 per day so.... yeah.. not sure which gameboy advance games are compatable though since i havent tried..
Anyways this game has a new story that will keep you amused, new bad guys, new Pokemon, almost new everything, think of this as a hand held, masterpiece
its what you call a game with a ton of new Pokemon, and i mean loads, over a 100 new ones
also you can exchange friend codes and battle online, put Pokemon up for trade etc