I’ve said it before, but I would love to see John Varley’s “Gaia” trilogy (Titan / Wizard / Demon) brought to the big screen, and I think they have the technology now where they could pull it off.
I would love to see a proper John Carter epic, and Doc Savage, and as long as I’m dreaming I want a pony for Christmas!
I haven’t gotten around to Doc Savage, but I love John Carter too much to want Hollywood to get their hands on him. When I read the novels, I kept thinking about how they would translate on screen, and I don’t think it would be effective. Without ERB’s wonderfully livid prose, it would just be one action sequence after another. And Hollywood’s done them all already. Superhuman acrobatics, floating ships, swordfights in space–Lucas stole all those for Star Wars, and The Lord of the Rings had huge hoards of CGI Martians–I mean Orcs. There’s just nothing left that would make a JC movie seem anything but derivative and boring now.
Of course, if they show Deja Thoris right, I’ll be there anyway!
George R.R. Martin’s wonderful, funny, fascinating, clever short-story collection Tuf Voyaging could make a terrific series of movies.
Or how about Asimov’s Foundation Trilogy? Or his Three Laws of Robotics stories? (Harlan Ellison did a kickass screenplay, now available in book form).
Hero? House of Flying Daggers? Curse of the Golden Flower? 
Maybe if someone like James Cameron directed it. But more likely it would be to Starship Troopers what Doom was to Aliens (the same…but worse).
No. Please don’t.
Personally, I keep hoping that Steven Spielberg can get Tintin off the ground. (He has rights to a three-picture deal.)
Found this at the IMDb message board for John Carter of Mars:
"As of 12/11/2006, comc book artist Rafael Kayanan was hired by Paramount to re-conceptualize “A Princess of Mars.”
Seems like the studio has reverted to the original project title and are trying again."
I have read the books (OK, just the first one, because the gimmick palled very quickly) and I absolutely despise Jim Carrey, but I thought the movie worked. Maybe my adoration of Meryl Streep balanced my abhorrence of Carrey.
Of course, you’d have to recast the kids at this point – at least Sunny. The twins who played her are now four years old!
It occurs to me that Dracula could be done effectively as a serial. In fact, it would seem less rushed if it were done that way. That was one of my many complainst about the Coppola version. He was racing through the material with barely a pause.
I’d like to see something new, strange, and unimagined, rather than a remake, sequel, or adaptation.
Something Discworld, I hope! 
The Dark Is Rising has a 2007 listing on IMDB, but I doubt it’ll do little more than start filming in '07 (if they even get that far). The audience is smaller than that of Narnia’s, but it could prove pretty popular if done with the same “feeling” of the books.
Also, here’s hoping that Whedon’s Wonder Woman gets off of the ground (without an invisible jet), and proves witty and franchise-worthy.
Some things should be left alone, I think.
I think the answer to the OP’s question would have been perfectly obvious if only The Hitchhiker’s guide to the galaxy movie had met our expectations. Sadly it did not.
Actually, if it were filmed properly it would be the worst movie ever made (being the worst book ever published), so I don’t see it becoming a series.
I am an incurable optimist. Utter incompetence in the past doesn’t, I think, always mean utter incompetence in the future. I have the heart of an eight-year-old child.*
I still hold out hope for a really good Dune serial. And I hold out hope that everyone will quietly forget the prequels written after the real author died.
*I took it from someone who was keeping it in a desk drawer. I plan to install Linux on it once I write drivers for all of the ventricles.
Between the Blade trilogy, the Underworld movies and the assorted Draculi films, the vampire genre has been done to death.
The AI thing has been done as well with The Matrix and Terminator movies.
If the Sci-fi channels Dune miniseries had more of the atmosphere and visuals of Lynch’s Dune, I think that would have been fine. As it stands, I think after two attempts, I think the window of opportunity has passed.
Quite frankly, I’m at a loss as to what kind of film they could make three of that would have the same level of “Holy shit I’ve never seen anything like that!” as well as the mass appeal as The Matrix, Star Wars or LOTR.
Battletech! CGI can easily handle it, tons of story arcs to work with, plenty of action, done well it could easily be another 5-6 movie star wars style franchise.
Stackpoles Return of Kerensky trilogy would be a wonderful run of movies.
I’d sit through an otherwise horrible battletech movie just to see the assault on Luthien done well.
I hope that NARNIA’s audience doesn’t lag as the series progresses, because I so want to see the film of THE LAST BATTLE (if they decided to just film that & THE MAGICIAN’S NEPHEW, I’d be content. I could make do with the PBS version of CASPIAN, DAWN TREADER & CHAIR, and no HORSE.)
Seconds for ATLAS SHRUGGED and a proper retelling of DRACULA.