Gutteridge also did a few unidentified illustrations: "a redraw of the Ecco 2 box art for a Mega Drive 2 bundle sleeve", a Jurassic Park poster illustration and a Streets of Rage illustration set in a subway. (Source)
Games
Other video game related works
Gallery
Sonic the Hedgehog 2 / ソニック・ザ・ヘッジホッグ2 (Mega Drive - 1992)
Promotional illustrations x2 (post-release) (Source: one was confirmed by the artist, the other by the owner of the original artwork)
Sonic the Hedgehog 3 / ソニック・ザ・ヘッジホッグ3 (Mega Drive - 1994)
Cover art for the European version: Knuckles illustration only (Source: mentioned in an interview by the artist + mentioned by the owner of some of his artwork)
Logo for the cover of the European version (Source: mentioned by the artist, via Mark Hughes)
Sonic Triple Trouble, AKA Sonic & Tails 2 / ソニック&テイルス2 (Game Gear - 1994)
Cover art for the European version (Source: mentioned in an interview by the artist)
.Note: artwork very similar to the one painted by Greg Martin for the US version
1993 Sonic calendar
Illustrations (Source: mentioned by the owner of the original artworks: 1, 2, 3, 4, 5, 6, + original artworks auctioned: 1, 2)
1994 Sonic calendar
Illustrations (Source: confirmed by the artist, via SonicRetro)
Sonic the Hedgehog 2
Sonic the Hedgehog 3
Sonic Triple Trouble
1993 Sonic calendar
1994 Sonic calendar
Sonic