From Planet Gamecube:
Sonic Adventure DX
Sonic Adventure was Sonic the Hedgehog’s first 3D game on Dreamcast, a pretty major event. Combining speedy platform gaming with exploration with characater-interaction, Sonic Adventure allowed you to play as Sonic and his many friends in a game that was simply huge. As of yet, there are no details on if/how much the game will be updated for the GameCube.
Screenshots
Sonic Pinball Party
Do you like Sonic? Do you like pinball? Well Sonic Pinball Party is set to offer up a host of different pinball levels based on Sonic characters, and NiGHTS is making a special guest appearance.
Screenshots
Source: Planet Gamecube