Tadashi Takezaki/SEGA
Sonic Adventure (1998) Public Relation
No further Sonic credits
Takashi Iizuka/Producer
Sonic Adventure (1998) Director, Character game designer, Field designer, "Chaos" game designer
Sonic Adventure 2 (2001) Director, Field Designer (Level Designer), Enemy Game Designer
Sonic Heroes (2004) Director, Level Designer, CG Movie Director
Shadow the Hedgehog (2005) Director, Lead Game Designer, Level Designer, Scenario Writer, CG Movie Supervisor
Various other Sonic credits, including Colours producer and Generations producer
Jun Senoue/Sound Director
Sonic Adventure (1998) Lead music composer, Sound director, Music produced by, Guitars, Keyboards
Sonic Adventure 2 (2001) Music Composer & Lyrics, Sound Director, Music Producer
Sonic Heroes (2003) Sound Director, Lead Music Composer, Sound Effects, Recording Coordinator
Shadow the Hedgehog (2005) Sound Director, Lead Music Composer, Sound Effects, Recording Coordinator
Sonic Generations (2011) Sound Director
Lots, lots more Sonic credits, mostly when working under Iizuka's leadership
Kazuyuki Hoshino/Art Director
Sonic Adventure (1998) Art director, Lead field artist, Enemy character designer
Sonic Adventure 2 (2001) Art Director, Player Character Designer, Enemy Character Designer, CG Movie Director
Sonic Heroes (2003) Art Director, Enemy Designer, Story Board Designer
Shadow the Hedgehog (2005) Art Director, Character Designer, Enemy Artist, Weapon Artist, CG Movie Supervisor
In recent games like S4, Generations and Unleashed, he's merely been credited under "special thanks". He's not very involved with Sonic games these days