Pokemon Diamond and Pearl are simply the finest iterations of Nintendo's hit franchise. Among the finest games on DS.
How? Nintendo has wisely allowed for connectivity between the Gameboy Advance titles and Diamond/Pearl, all using one DS. This is perhaps the games' greatest triumph. At long last, multiple generations are tied together such that all three (Fire Red/Leaf Green, Ruby/Sapphire/Emerald, Diamond/Pearl) feel like parts of the same universe. Moreover, even antisocial gamers will be able to amass a huge collection of Pokemon via the new trading system. Nintendo has not only managed to create a logical purpose for their GBA rehashes, but has also opened up a wide range of gameplay possibilities.
Even better, gamers can now trade with anyone in the world via the Global Trade System. While a wireless internet connection is of course required, this is obviously an incredible step forward for the series. While not perfect (the glut of players asking for level 100 legendaries for their Wurmples is staggering), it's much-appreciated.
But what about the core game outside of these two improvements? It's pretty much more of the same; battles take a bit too long, even with animations turned off, the graphics, while aesthetically pleasing, haven't technically moved very far beyond the GBA versions, and the cookie-cutter "fight 8 gym leaders, go to Pokemon League" system is in full effect here, even with the same town archetypes. That said, the world is actually better from a design standpoint than Ruby and Sapphire, so that's nice. Even though it doesn't feel incredibly new, it works quite well.
In short, even if you haven't taken the Pokemon plunge before, this is a game you must own. Forget the "kiddie" label; Diamond and Pearl are surprisingly deep and provide hours upon hours of gaming bliss.