worried that my wii may be scratching my disks and i need a good shooter game

so i play my wii reguarly, always put the disks back in there case (never leave them in the console while not in use) and i try to keep my play area dust free. But there is one somewhat large scratch on my copy of Zelda: TP. No one else in my house plays my wii and i always keep it in the case. Is there an explanation for this? is it the wii or something else? The flap for the disk drive is somewhat dusty but its not terrible. Also are there any good shooters beside red steel? I don't wanna drop the 40-50 on it and have it go on sale. Also is excitetruck worth it?

thanks a bunch