Maybe I should move on; its been almost 14 years.
But the first movie that comes to mind when I think of D&D is the stupid D&D movie from the year 2000. Why couldn't it have been Lord of the Rings, or Conan the Barbarian? Anything but Dungeons & Dragons: The Movie.
Because neither of these movies tried to fit the plot and story into the context of a game, and neither had a Wayans Brother make a smartass remark in every scene he was in.
It was almost all too reminiscent of what happens when things digress too much at the gaming table, when players say they're playing D&D but instead jack around, quote Monty Python, and generally waste time. Meanwhile, the DM sends half-baked villains at the party that nobody takes seriously, all the while trying to cover up his plot holes with accessories ("look my new"--badly--"painted miniatures", which equates to the CGI in the movie, or Damodar's lipstick.)
Even worse, the movie actually turned off a prospective player to D&D. He played wargames, but wasn't sure about D&D. But he figured that the D&D movie might be somewhat representative of what happens in a D&D game. So we went to see it.
I came out of theater shaking my head. He came out saying, "Nah, I think I'll pass..."
But my games aren't like that! Really, they're not!
I think I let out a little cheer in the movie theater when Snails died.
EDIT: Here's how they could have made the movie better.