There is a pretty good article pondering the same question that many of us gamers have been pondering for years, "why can't they make a good D&D movie", over at Spinoff Online.
The author, Graeme McMillan, makes many of the same points I've seen repeated over and over around the net. The D&D name has almost as much recognition as many other big budget properties like Transformers and Star Trek. Plus there is a built in fanbase waiting for a good film. Why there has been no Lord of the Rings level D&D movie yet is beyond me.
As McMillan writes in the article, since Hasbro owns G.I. Joe and Transformers as well as a movie studio, there really is no reason that this movie isn't being made. Unless it is due to rights disputes or just fear of making another dud. Perhaps because there is no well defined story or characters that are recognizable to non-gamers, like in many other franchises, no one really knows what to do with it.
I'd be happy with a live action Forgotten Realms movie starring everyone's favorite Drow or even a live action Dragonlance movie. Although my personal preference would be an Eberron movie, but it is more likely they'd go with a "classic" D&D setting over Eberron. All I know is I want this movie. Hell, I want 10 of them, but only if they are good.