While I agree with you, I think the main hurdle facing any DnD movie is the fact that it will probably be seen as a LOTR wannabe by people who are not DnD fans. Let's face it - Orcs, Elves, Dwarfs, Halflings etc., are fundamentally ripped from Tolkien's vision of such things, with Halflings taking the place of Hobbits, so they will inevitably be viewed in that context in a DnD movie. Which unfortunately gives it an 'also-ran' feel, in spite of all the 'original' content in the DnD universe.
Anyway, I rented the original DnD movie on video once - and I actually fell asleep about half an hour into it. Gripping stuff. They definitely need to get away from the DnD cartoon production mentality and focus on a more mature audience.
As for the suggestion to use NWN to make a 'long cutscene', you're talking about machinima - using game engines to tell stories. There have been quite a few well-made fan movies like this, so it would be intriguing to see someone develop something like that using the NWN engine. Of course, I think some custom animation wouldn't go amiss - because I couldn't handle watching the same looping animations that they used in the HotU cut scenes. I'd go mad. No...seriously.