UPDATE!
I have updated the list with some new information. Interesting notes:
- Although Sonic 3D Blast was developed by Traveler's Tales, it was designed by Takao Miyoshi who is responsible for the Phantasy Star Online/Universe series.
- Although Sonic R was developed by Traveler's Tales, it was designed by Takashi Iizuka, who every one should know who he is.
- Although The Sonic Rivals games were developed by Backbone Studios, they were both designed by Takashi Iizuka.
- Although most HandHeld Sonic games have been developed by Dimps, most of them have been designed by Akinori Nishiyama, who works at Sonic Team, not at Dimps. He has also been involved with other Sonic Team games, like the Sonic Adventure series and others.