PS2 adapter doesnt work for XBOX 360.

I was at gamestop yesterday and found the PS2 to PS3 adapter...........which takes the PS2 male end and adapts it to a USB plug.  I have Guitar Hero 1 on PS2, and Guitar Hero 2 on XBOX 360, and I wanted to see if it would possibly work.......... it didnt...........so, it looks like I"m gonna have to buy another guitar controller for the 360, so we can do the multiplayer thing