There are 15 achievements worth a total of 250 points
Become friends with Tails.
Become friends with Knuckles.
Become friends with Amy.
Become friends with E-102.
Become friends with Big.
Clear the Sonic story.
Clear all characters stories.
Get Level A on all the Action Stages.
Get all Emblems of the Sub Games.
Get all Emblems of the Chao Race.
Get all Emblems in the Adventure Field.
Get all 130 Emblems.
Get all 130 Emblems by playing Sonic Adventure DX. (DLC: Sonic Adventure DX Upgrade table)
Get Level A on all the Action Stages by using Metal Sonic. (DLC: Sonic Adventure DX Upgrade table)
Clear all 60 missions. (DLC: Sonic Adventure DX Upgrade table)