Actually, ERUNT backs up your registry only. System Restore backs up your registry and a few other things.
If you already back up all of your files via a different method and are solely looking for a registry backup method, ERUNT may be able to replace system restore.
Personally, I have a system image which is a carbon copy of my hard drive in it's infantile state. It has all of the basic information contained on it. I also have a backup of all my passwords in a password management database. I have backups of all my media files on secondary external hard drives.
Basically, you need to choose what type of backup you're looking for and then you can choose whether you want ERUNT, System Restore, or a a complete system imaging tool.