Going through Sonic Team's official game timeline, the following games are absent/non canon:

Sonic Pocket Adventure
Sonic Advance
Sonic Rivals
Sonic Rivals 2
Sonic and the Secret Rings
Sonic and the Black Knight

Is there any reason in particular these games are excluded from the timeline? The storybook games were mentioned in Generations so I assume those are an oversight. The Rival games weren't release in Japan thus I believe that may be why they are excluded. Sonic Advance, no fucking clue. Sonic Pocket Adventure, might be a legal thing with it being on the Neo Geo Pocket.