The first pair of games on the Nintendo DS, Pokémon Diamond and Pearl brings players to the Sinnoh region. Dominated by the central mountain, Mount Coronet, players must embark on a journey to become a Pokémon master, while dealing with the evil schemes of Team Galactic, and their enigmatic leader Cyrus. Featuring new Pokémon, new battle mechanics, and for the first time in the franchise Wi-Fi play thanks to Pokémon Underground, players are connected more than ever in Pokémon Diamond and Pearl, making it one of the largest generations yet for the franchise.
From the game's Wikipedia page:
"Pokémon Diamond Version and Pokémon Pearl Version are role-playing video games developed by Game Freak, published by The Pokémon Company and Nintendo for the Nintendo DS. They are the first installments in the fourth generation of the Pokémon video game series. Originally teased in 2004, they were first released in Japan on September 28, 2006 and later released in North America, Australia, and Europe over the course of 2007. Pokémon Platinum, an updated version, was released two years later in each region.
Like previous Pokémon games, Diamond and Pearl chronicle the adventures of a young Pokémon trainer as they train and battle Pokémon while also thwarting the schemes of a criminal organization. The games add many new features, such as Internet play over the Nintendo Wi-Fi Connection, changes to battle mechanics and Pokémon Contests, along with the addition of 107 new Pokémon. The games are independent of each other but feature largely the same plot and while both can be played separately, it is necessary to trade between them in order to complete the games' Pokédex.
Development of Diamond and Pearl was announced at a Nintendo press conference in the fourth calendar quarter of 2004. The games were designed with features of the Nintendo DS in mind. It was forecasted to be released in Japan in 2005, but ultimately shipped in 2006, the 10th anniversary year of the franchise. In promotion of the games, Nintendo sold a limited-edition Nintendo DS Lite in Japan, and held a release party celebrating their North American release.
The games received generally favorable reviews. Most critics praised the addition of Wi-Fi features and felt that the gameplay, though it had not received much updating from previous games, was still engaging. Reviewers were divided on the graphics, however, and the audio was criticized as being primitive. The games enjoyed more commercial success than their Game Boy Advance predecessors: with around 18 million units sold worldwide, Diamond and Pearl have sold over 2 million more units than Pokémon Ruby and Sapphire and almost 6 million more units than Pokémon FireRed and LeafGreen, while also outselling their successors, Pokémon Black and White, by over 2 million copies. The games are one of the most successful Pokémon games of all time."