Am going to "assume" your applications are the same in Leopard that they were in your Tiger install and backup or that you have the disks to re-install any new ones you have installed under Leopard.
Am also "assuming", that you still have your SuperDuper bootable Tiger back up and that you did verify it was functional after you created it.
I also agree with the above, would not go back to Tiger unless you have an issue with an app you must have and it is not yet Leopard compatible.
1. Either move all the new files you want to keep that are not on the backup to the 2nd partition of that drive, another drive, or burn them to disk.
2. You will then need to boot to your Tiger back up by holding down the option key during startup and choosing the back up.
3. Once booted back in Tiger, run SuperDuper just like you did to create the backup. From your comment above, it sounds like you tried running SuperDuper from Leopard. This would cause the Mac HD to be greyed out, as you cannot select the volume you're currently running in as the back up destination. And SuperDuper is not yet Leopard compatible.
4. Re-install the new files and apps.