Oblivion on Xbox 360 won't work?

When I turn the Xbox on the game part just says open tray, even though the game is in there, then I open it then close it and sometimes I get a black screen then a window pops up that says the disc is unreadable and to either clean the disc or restart the Xbox I have tried both :( , the game has NO scratches apart from one on the ring closest to the hole (not the plastic, the silver part that says Xbox), is this the problem?

to see if it was the disc or the Xbox I put a different disc in and it worked then I put the oblivion disc in my computer to see if it would even come up and it did so the disc is obviously readable, what can I do to make it work on the Xbox?