Even after all these years, Pokemon is still somewhat good.
Its actually been about nine years since Red and Blue first came out, and spawned the Pokemon craze. After the fad died down, the cards, the show, the merchandise. Here we are in the fourth generation of the handheld RPG Pokemon games. Its actually pretty good.
The game starts off as any other Pokemon game. Your about to become a Pokemon trainer. You get to pick between three starter Pokemon, which are always Grass, Fire, or Water types. Then you leave your hometown and collect badges, then collect all 8 to challenge the Elite 4/Current Champion to become the Champion. While also trying to thwart to villians plans which are usually always called Team *Insert some name here* (Team Galactic in Diamond and Pearl). Yes we know this "Story" oh too well.
So what's really different? Well several things. They changed graphical style up a bit. Now the world is somewhat 3D. The buildings, trees, and mountains for example are 3D but mostly everything else is still 2D in that GBA art-style. The game uses Pokemon animations in the beginning of battle like in Pokemon Emerald. It uses the touch screen to select commands which you can use a stylus or just use the traditional controls, which gives the top screen a bigger view of the battle then having to fit both on one screen. Of course theres a whole new set of new Pokemon.
Another feature D/P has is that you can eventually obtain the National Pokedex (taken from Emerald, Fire Red, and Leaf Green). This can be obtained when you have seen all the Pokemon in the game native to Sinnoh excluding some Legendaries and evolutions of Pokemon from past games like Electivire, Magmortar, Rhyperior (which are evolved forms of Electabuzz, Magmar, and Rhydon). When you receive the National Pokedex you can catch Pokemon in Sinnoh from previous games and even migrate your old Pokemon from Ruby/Sapphire and Fire Red/Leaf Green via the Pal Park. In my opinion this is one of the best features in the game.
On the online multiplayer/local multiplayer front. They have changed a lot. Diamond and Pearl is the first handheld Pokemon game where you can play agaisnt people across the world in either battles or trades (with voice chat) using friend codes. There is also a place called GTS where you can either search for a Pokemon to do a trade or put up a Pokemon for trade. It is totally anomonious. In my experience the best way is to put up a Pokemon for trade (and put what Pokemon you want for it), go to sleep, check the next day or couple days and you should receive the Pokemon you wanted in the trade. GTS is definetely a great edition for people who don't have too many friends to trade with.
In the end. Its what you expect from a new Pokemon game. New Pokemon, some new features, etc. If your not someone who'd didn't like playing Gold/Silver, and Ruby/Sapphire after Red/Blue then this game isn't for you. If your someone who has played at least one Pokemon game every generation and liked it then this game is for you. It doesn't add much to the franchise but it continues to do what it does best, and thats being addicting.