just use dvd shrink! in teh "save target to" box, choose image (I don't have shrink on this computer, but it's something similar to that)
and, all a dvd IS is a "audio/videoTS folders filled with files" that's what the ISO will contain the image of, so saving it as files works exactly the same.
dvd decrypter in "ISO>READ" mode will also output to ISO
ImgToolClassic will also make an ISO I think.
there are tons of options. Use what you're comfortable with.