There's a little trick I use on cd's, so it should by all rights work on ps2 games, even though they are dvds. As you may or may not know the actual part that has the data inprinted on it is not the bottom surface but actually the top most layer of the disc. So for finer scratches all you really need to do is buff em out. Go out to your garage and get the car wax. Apply a little and with a nice soft cloth buff the scratch right out. It works on car paint, and it works hella good on cd's.

Infinite