You know, only twice did I need backups of games I owned. 1 was physically broken by a person in my family (super smash bros melee), the other though was a fault of the horrible packaging, which cracked the disks in the middle (first PC version of GTA San Andreas bought at 50€).
In fact I thought it was my fault, so I bought the game again (at 30€), only to have it crack once more. Finally they released the game with a normal case, and I bought it for a 3rd time (at 20€). Perhaps I should have contacted them for a new copy of the game, or a consumers organization if they refused, but I didn't bother.
As you see backups just didn't do it for me, I
had to have the original pretty disk. So if I want to pirate GTA5 to see if it's any good, I have every ethical right to do so

. 3 copies of GTA SA and 1 copy of the horrible GTA4