Cheats for Guitar Hero 2 on the Xbox 360 are entered on the main menu, where you see options for Career and Quick Play. See additional notes after the cheats list.

Unlock All Songs
Guitar Hero 2 cheat code: Blue, Yellow, Orange, Red, Yellow, Orange, Blue, Yellow, Blue, Yellow, Blue, Yellow, Blue, Yellow, Blue, Yellow
Note: This is the unlock all songs cheat for the PAL (Europe) version of the game.

Unlock All Songs
Guitar Hero 2 cheat code: Blue, Yellow, Orange, Red, Orange, Yellow, Red, Yellow, Red, Yellow, Red, Yellow, Red, Yellow, Red, Yellow
Note: Note: This is the unlock all songs cheats for the NTSC (America's) version of the game.

Special note about Guitar Hero 2 cheats on the Xbox 360.

• Guitar hero cheats from the PS2 version do not work on the Xbox 360.
• The effect of using Guitar Hero 2 cheats may or may not effect the earning of achievement points.
  achievements can still be unlocked by using the above cheats.
• Re-entering a cheat code for Guitar Hero 2 will result in de-activating the cheat.
• You can have more than one cheat active at the same time.
• You do not need to hold the select button to enter a cheat, simply enter it while at the main menu screen, rather quickly. It should take around three seconds to enter one of the codes.

Link to GH2 360 Cheats