Ok, since I can fly through these, here's my opinion on Dreamcast Era's canon.
- Sonic Adventure
- Sonic Advance
- Explaination: Since only a passing reference of SA1 shows up in SA2, I think something just as notable must have happened for no one to largely refer to SA1.
- Sonic Adventure 2
- Sonic Advance 2
- Sonic Heroes
- Sonic Battle
- Sonic Advance 3
- Shadow the Hedgehog
Since the Dreamcast Era is very linear in how it works, having the 2 Adventures and 3 Advances pretty much back to back, I had my work cut out for me. I put Heroes right before Battle because I think Battle may have had a reference to Heroes, not sure since I haven't actually played Battle. (I actually got that info from this wiki =P) Modern will be up soon, which I actually have to put effort into. Comment as you wish.
EDIT: Ok, fixed the error of putting Battle after Advance 3 and moved Advance to explain why no one mentions SA1's events largely in SA2.