Can it read other games?
If yes, then your MW2 disc might have a crack/scratch. Will need replacing.
If no, your Bluray Drive is gone and you'll need a replacement from Sony.
I hope for your sake it's the first!
If the BluRay Drive is dead, then don't ask sony for a replacement, they will charge an arm and a leg, try
The same happened to me and it cost me £99 to get repaired via Console Doctor which compared to what sony offer is far better.
sounds like the drive has failed. The same thing happened to me:
you put the disc in, blue-light comes on but the game/video doesnt show on the list (where it should be).
However check with other games/dvd's/cd's etc. to make sure. It could be the disc? I had one of those fail on me too!
Roguey's PS3 Site