Ok, I'm going down in flames here, but I sort of liked the D&D movie. It wasn't high comedy or drama, but there aren't nearly enough quality sword & sorcery type fantasy movies out there to compare it with. All of them suck rocks. The best is probably Ladyhawke, and that was what, 20 years ago?
If you list the top 20 fantasy S&S movies out there, that aren't sci-fi-based (no Star Wars), I'd be hard pressed not to include "Dungeons & Dragons." I too thought it was abysmal, but it was better than "Hawk the Slayer" and a host of other mediocre examples. Some of it's personal taste, but I hate Willow, even though I like everyone involved in it. Ron Howard once said about Willow, "No one sets out to make a bad movie..." I think the same could be said of "Dungeons & Dragons." The movie-makers misjudged their target audience, tried to include enough flashy kiddy stuff to satisfy a larger segment and wound up alienating many of the hobbyists.
Production values need to go up and writing needs to get better. Hopefully LoTR will help both of those by showing Hollywood there's money to be made in this genre.
In the meantime, I'm going to enjoy my VHS copy of "Dungeons & Dragons" as much as before and hope things get better for fantasy movies, but not mock those who at least tried to make a decent movie.