You may be missing a small detail in trying to properly input the code...make sure that you are:
1) Allowing the demo to run until it gets to the High Score Screen
2) On the High Score Screen, input a full counter-clockwise circular motion that starts with pushing right and once you get back to right again, move the controller into the down-right position and hold while you press A, then B, then C.
3) You should hear Geese's voice taunt you if it worked.
Just keep practicing and you should get it before long. Even if you screw up, the code will still work if you can complete the code correctly on the High Score Screen.
EDIT: And I have this on NEOCD, so keep the faith...
