It’s a real movie (barely, judging from the trailer), but it’s got nothing to do with Diablo III other than having “devil” in the title. It’s some sort of modern day cops vs. drug dealers drama, and the ripped off cover artwork is inexplicable; probably it just looked better than any photo from the movie would have.
I like the title they added with the movie’s name; they couldn’t get the same font, but they found one that sort of matched, thematically. Not so with the point size or color or golden shine, though. I guess when you’re producing DVD box covers that are copyright infringements and will get nuked as soon as Blizzard’s lawyers finish their morning 18, there’s no real point in sweating over every little detail.