I still feel that this is a problem that WotC would love to have.
That's for sure.
The real problem, though, with marketing D&D stuff, as compared to Marvel, is that Marvel is about stories, stories that have in many cases been repeated to the point that they've virtually cultural touchstones (at least for some significant minority of the population). The same is true of LotR and many other properties. You say you don't think most people were familiar with the LotR novels, I note. I think that's both true and false. It's true, I think, that most people in the audiences hadn't actually read all of the novels. However, I would suggest that most people in the audience were either going with people who had read some or all of the novels, or were least culturally familiar with them, aware of the general themes and so on.
With D&D, it's a game, not a set of stories. There are no real general themes to be culturally aware of (or if they are, they're game-y stuff, like about the fickle-ness of DMs, or the weird dice) Whilst there are novels attached, and they've sold well, they don't have a huge rabid fanbase, nor a youthful fanbase (who are the most useful fanbase for getting bums on seats in cinemas, generally, and importantly, selling merchandise), nor, further, does that fanbase necessarily cross over strongly with the fans of the game. The D&D novel fanbase is perhaps more comparable with the fanbase of the EU Star Wars novels (recently disregarded as irrelevant by Disney, and logically so, I think), or the Star Trek novels. But smaller.
So there's no "story, eternally told" for D&D to leverage to build it's brand.
That makes it a very tricky prospect, movie-wise.
Not to say that it's impossible, but I think you'd really want to write a strong movie, then brand it D&D in the opening credits, Marvel style, and actually try to avoid mentioning D&D in the marketing (the people who care WILL already know).
Even in computer gaming and the like, D&D is a weak brand these days. It has been superceded, essentially by world/setting/aesthetic brands, like Dragon Age, Elder Scrolls, or Warcraft. Putting D&D on a game is a way to get people to look at it a bit more than usual, but they will not be expecting brilliance (most D&D games in the last 10+ years have been pretty mediocre or outright bad), and there is little reason to pick D&D over another brand.
D&D could could counter this by marketing itself setting first, brand second. I could very easily see "Forgotten Realms" or "Dark Sun" becoming big, popular brands, if WotC could get a company to actually make a good, aesthetically striking game set there (and simplify the settings to the point where they were accessible and distinctive). "Ravenloft" might be another option - I suspect gothic will make a comeback in the next half-decade or so (TV is already moving that way with Penny Dreadful, Constantine and the like).
The big problem in gaming is, though, the precedent Bioware set with Dragon Age. They explicitly decided to avoid using D&D, and to create their own IP, so they were beholden to no-one. And it worked. And now it seems like anyone creating a fantasy game simply goes with their own IP, rather than trying to license one, despite so many being available - the one recent except being Numenera, and I suspect that was solely because they "got in on the ground floor" with that on.
This is an increasingly common view in the games industry - Bobby Kotick from Activision recently noted that a significant reason that Destiny is an original IP was to prevent them ever being beholden to anyone (something like "If you're risking $500m, you want to do it with your own IP").
To be clear, I'm not saying "Don't try!", but I am saying that WotC will need a very clear strategy, and quite a lot of luck to really get anywhere with this. I definitely think that their current track with D&D, which is to say making the FR the default setting and paying concept art specialists to create the art, and attempting to give it a distinct, consistent style, is a good first step if they want to be successful with this. They will need to look to the long term, though, and really rebuild the brand quite carefully - I'd be particularly keen that they avoid allowing any more mediocre or bad games or movies to use the D&D or FR brands.
