I use DVDdecryptor with "ignore errors" feature turned on and retries=2. This can recover most of a movie. Transcoding it with NeroVision (or a dvd editing tool) will remove any timing errors.
For games, it is much more difficult. You will need some data-recovery software.
Or, if you have the original disc, you can mail it to the publisher for a very inexpensive replacement. You have already paid for the license, the publisher will only charge for materials and shipping (a mimimal price).
If the disc has blotching, which is a liquid-looking appearance of the data layer, it is more difficult to recover. But, if the disc is merely scratched, there is a special wax that can be applied to make the disc readable. Most movie-rental stores have this scratch-wax available for purchase.