Pokemon Diamond and Pearl are great
The Wifi options are great. Battling with your pokemon against friends or totall strangers is one of the best things of pokemon DP. The new pokemon game Pokemon Platinum is promising a new kind of Battle Frontier so getting Wifi will be even greater. There is also said that you can get Wifi with the Undergrounds.
To get all pokemon on your pokedex is taking a long time without cheating. I`ve done it though. But that`s one of the reasons you can get addicted. Many people say that Pokemon is just for little kids. But that not true. Most people who play Pokemon are teenagers, because pokemon is also a stragety game. Little kids just do an attack without thinking of the consequenses. Like Hyper Beam, it sounds strong but it will take two turns.
Pokemon DP is a great game with many options and it was worth playing it. I`m waiting for Platinum to come now. I will try to get the Japanese version first to get a good look at the game. The story will come to me in the English version.