IMO, they don't have enough variety for Sonic's music. Here's my ideas:
O - Original
R - Remix
Green Hill Zone (O)
Angel Island (R) (rock)
Game Select (Sonic 3) (R)
Final Boss (Sonic 3) (R) (chorus)
Live and Learn (O)
Emerald Town (Sonic Battle) (R)
Chemical Plant (O)
Chao Garden (Sonic Adventure 2) (R) (rock)
More suggestions?
O - Original
R - Remix
Green Hill Zone (O)
Angel Island (R) (rock)
Game Select (Sonic 3) (R)
Final Boss (Sonic 3) (R) (chorus)
Live and Learn (O)
Emerald Town (Sonic Battle) (R)
Chemical Plant (O)
Chao Garden (Sonic Adventure 2) (R) (rock)
More suggestions?