Like I said, it's impossible. No matter how hard you secure your content on media, it can be copyable. The trick is to make the content worth money in people's eyes. Case in point: I purchased Air's Talkie Walkie album a few years ago, and it came with a DVD of their tour. Things like this make people want to spend money on your disc.
Unfortunately, DVDs aren't any different than games, and I would argue that DVDs are easier to copy than software, because the standard is set in stone. If you want your DVD to be playable in DVD players, then by that same token it can be easily copied.