Yes, you can burn an ISO to a DL disk. You just have to use the right tools.
First off, don’t use anything other than Verbatim DL media. Some other types are acceptable, but the quality varies too much for recommendations, so it is safest to use Verbatim.
Second, you’ll need a good decryption/ripping program. If you are trying to back up newer movies with more advanced protection schemes, you’ll need a program that is still being updated. That means either DVDFab or AnyDVD. There is a free version of DVDFab, called HD Decrypter, but if you use it, you won’t have a free trial of the main program…just a heads up on that. http://www.dvdfab.com/free.htm
In any case, rip the files to the hard drive. Then build and burn the ISO with ImgBurn. Here is the guide for building the ISO and MDS file: http://forum.imgburn.com/index.php?showtopic=1777 Use the MDS file as input and burn to the disk using ImbBurn in Write mode. Burning Verbatim DL disks at 4x seems to be a fairly safe choice these days.
Or you can have it output straight to the burner, as shown in this guide: http://forum.imgburn.com/index.php?showtopic=4643