Board Thread:Questions and Answers/@comment-27511601-20161013215409/@comment-679780-20161014012158

I believe Sonic Generations is just as canon as Sonic Unleashed, Sonic Colours, Sonic Lost World and upcoming Sonic '17.

However it should also be regarded as a "tribute game", as in it was mostly made for the nostalgia of the franchise. But it still has it's own story that is regarded canon than Sonic going throw past stages for the heck of it.