Hmmm, I tend to disagree.
It is a technicality but you are entitled to create a backup of 'your own' game discs. If you download it then it would not technically be a backup of your own disc, it would be a backup of someone elses disc! Like I said it is a technicality.
Plus I dont think downloading games should be encouraged, it is better to learn how to do your own backups, even if this requires you to purchase the right hardware to do so. (meaning having the correct burner).
If you start the habit of downloading games then it could be very easy to fall into bad practices.
Thats just my interpretation of the laws etc.