This code unlocks everything in the game. Absolutely everything in the game will be unlocked when you enter Select, Down, R2, L1, R1, L2 at the title screen.
Defeat Arcade mode with Wolverine and Psylocke will be available.
Defeat the game with every character, including Psyclocke, and you will unlock Juggernaut.
Unlock Professor X
To get Professor X, beat the arcade mode with Juggernaut. Then select Magneto and press L1.
To play as Spidey, defeat him in arcade mode and then complete arcade mode. After you beat Arcade, select Cyclops and press L1.