Accomplish the indicated achievement to get the corresponding number of Gamerscore points:

Sonic Finale (25 points): Complete the game as Sonic.
Knuckles Finale (25 points): Complete the game as Knuckles.
Please Continue (25 points): Earn a Continue in either a Bonus or Special Stage.
Gettin' Super (25 points): Collect all seven Chaos Emeralds.
Chaos Emerald (15 points): Collect a Chaos Emerald.
Hot Feet (15 points): Finish the Lava Reef Zone.
Desert Runner (15 points): Finish the Sandopolis Zone.
Sonic Finale (25 points): Complete the game as Sonic.
Grease Monkey (15 points): Finish the Flying Battery Zone.
Knuckles Finale (25 points): Complete the game as Knuckles.
Fun Guy (10 points): Finish the Mushroom Hill Zone.
Extra Hedgehog (10 points): Collect 100 rings.
Two Sided (10 points): Start the game once as each character.
Extra! Extra! (10 points): Enter a Bonus or Special Stage.
Please Continue (25 points): Earn a Continue in either a Bonus or Special Stage.
Gettin' Super (25 points): Collect all seven Chaos Emeralds.
Chaos Emerald (15 points): Collect a Chaos Emerald.
Hot Feet (15 points): Finish the Lava Reef Zone.
Desert Runner (15 points): Finish the Sandopolis Zone.
Grease Monkey (15 points): Finish the Flying Battery Zone.
Fun Guy (10 points): Finish the Mushroom Hill Zone.
Extra Hedgehog (10 points): Collect 100 rings.
Two Sided (10 points): Start the game once as each character.
Extra! Extra! (10 points): Enter a Bonus or Special Stage.