what sega game is similar to grand theft auto?

Answer 1

That game would be called Yakuza, for the PS2.

Background:
Yakuza is an action-adventure title with a story and setting focusing on the darker side of Tokyo life. In a society where respect and honor holds great importance, there is an even higher regard for these traits within the one organization that is most feared by all: the Yakuza. Kiryu Kazuma – a former rising star in the Yakuza who is rebuilding his life after serving a 10-year prison term for murder – suddenly finds himself caught in a spiraling underworld plot involving a mysterious girl known as Haruka and a missing $100 million. Kazuma must use his fists and his wits to stay alive as he unravels the complex web of truth and lies that surrounds the notorious Yakuza. The game is produced by Sega's Toshihiro Nagoshi, collaborating with Japanese author Seishu Hase as scenario director.