Ok, Taranaich...What exactly is it you want? First you bag on Fafhrd and Mouser as being too "witty" and lacking the grimness of Conan. Then you turn around and say "Worms of The Earth" is "repressive and dark". I'm guessing you do "like" the B M M stories? Or don't you?
I like my fantasy dark and gritty, therefore "Worms of the Earth" is one of my favourites.
As far as marketability? Well take "Mystic River". Clint Eastwood, Sean Penn, and the rest. Dudes best friend is abducted right before his eyes. Raped by two men for a period of time. Escapes and is never the same after. They all grow up. The two are neighbors. Sean Penn"s character, his daughter gets killed. The hunt is on to find out who done it. Sean's character for various reasons begins to suspect his child hood friend. Ends up killing him in cold blood. Finds out it wasn't him. HOw's that for tragic and grim. Or repressive. BTW, excellent movie.
Difference is, Mystic River is a drama. It does not have the stigma of fantasy films being either inoffensive family flicks or trashy gore flicks. It also has Eastwood and Penn, two accomplished and respected actors. It's like "The Woodsman" or "Deliverance": both deal with very unpalatable and repellent subjects (paedophilia and rape) in a realistic setting. As far as I've seen, the most popular modern fantasy films do not feature such discussions, although I'd be impressed if a good fantasy film did (they're making a film of Dan Simmon's "A Song of Kali" which is a truly harrowing story with a fantasy edge)
Having thought about it more, I think "Worms of the Earth" COULD be quite marketable if it was promoted as a horror a la Stephen King movies. If it's reasonably heavy on the supernatural and bloody aspect, it could become a cult favourite (which usually do gangbusters on DVD)
PS How about the Elric Saga. Pretty dismal, but would make an excellent movie.
If they were brave enough to do it as in the book. I know it's a kid's film, but I lost all respect for the "His Dark Materials" film once they took all references to religion out. I didn't necessarily agree with their rather ambivalent views, but I'd rather they didn't make the movie at all than remove it's soul (perhaps a poor choice of words). Most likely it'd end up sanitised like Earthsea.
Again, I'd like to stress I'd love to be proven wrong.