Sonic Advance: Beat with all four characters and got all chaos emeralds
 

What sucks is you only become supersonic for the final boss battle on the moon. Not like in the other games where you get 50 rings and can turn into him at any time. I'm majorly disappointed. :(

I feel your dissapointment man. I felt the same way when I completed the game. My reccomendation, fire up your old Genesis and pop in Sonic the Hedgehog 3.