I have bought multiple MW2 disks and none of them play for more than 5 minutes. every other game works... WHY?

Have you tried playing ANY other newer games like MW2? It could just be that your console is older and doesn't recognize the game or something. I have ahd this happen with a few games and was told the same thing, but yet I own and play MW2 so I can't be too sure. Try installing the game onto your Xbox hard drive and attempt to play then. That is what I had to do with Halo 3 and Halo 3: ODST.