There's already a perfect D&D
movie out there (that, for reasons I can't fathom, refuses to come out despite having been done for quite some time now). That's the kind of thing a good D&D movie would need to do; D&D is all about playing
the game, not reveling in the "awesome" (and I'm using that word quite wrongly) game worlds at their disposal.
Even the 80's D&D cartoon figured that out.
Unfortunately, they're more likely to try and go with a "straight" fantasy film. Again. Which will likely fail. Again. But, c'est la vie