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

  Complete the Game (25 points): Finish the game. 
  Fast Freeze (25 points): Complete the Icecap Zone. 
  Complete Chaos (25 points): Collect all seven Chaos Emeralds. 
  Points III (25 points): Score 80,000 points. 
  Marble Finishes (15 points): Finish the Marble Garden Zone. 
  Wet Feet (15 points): Run across water. 
  Wet and Wild (15 points): Finish the Hydrocity Zone. 
  Points II (15 points): Score 40,000 points. 
  Chaotic (10 points): Collect a Chaos Emerald. 
  Halfway there... (10 points): Collect 50 rings. 
  Goodie Gumballs (10 points): Get a blue gumball. 
  Points I (10 points): Score 20,000 points.