Board Thread:Questions and Answers/@comment-6858788-20150708003724/@comment-26973802-20150710230532

Going by my chronological order of the games, Sonic Unleashed is the last one to feature humans (besides Eggman) and human cities. Of the ones that followed:


 * Sonic Colors - Is set in an interstellar amusement park created by Eggman, and an alien planet


 * Sonic Generations - Is all levels from past games (more specifically Sonic the Hedgehog, Sonic the Hedgehog 2, Sonic & Knuckles, Sonic Adventure, Sonic Adventure 2, Sonic Heroes, Sonic the Hedgehog (2006), Sonic Unleashed, and Sonic Colors) due to the time travelling of Time Eater.


 * Sonic Lost World - Is set on a small planet Lost Hex. Earth is seen a few times but Amy, Knuckles, and Eggman were outside of a city at that time.

I guess we just haven't seen GUN since Sonic the Hedgehog (2006), even though Shadow is working for them now as erasing Iblis and Mephiles will not have changed that