Sonic Adventure (ソニックアドベンチャー, Sonikku Adobenchā?) is a video game created by Sonic Team and released on December 23, 1998 in Japan by Sega for the Sega Dreamcast and is the first game in the Sonic Adventure series. One of its development titles was Sonic RPG, (the final game was an adventure game instead, not a standard RPG)[citation needed]. The final updated edition, known as Sonic Adventure International, was released on September 9, 1999 in North America, October 14, 1999 in Japan and Europe, October 18, 1999 in Belgium, the Netherlands, and Luxembourg, and December 3, 1999 in Australia. A director's cut version was released in 2003 as Sonic Adventure DX for the Nintendo GameCube and in 2004 for the PC CD-ROM. It has sold over 1 million copies in the United States alone, making it the top selling Dreamcast game. It is the first ever Sonic game on a sixth generation console. Its sequel is Sonic Adventure 2.

Source: Wikipedia