But if any producers read HN and are looking for other well-developed fantasy or science fiction universes with plenty of existing written stories that could be turned into excellent TV series, miniseries, or movies, here are some that I'd definitely want to watch, and I don't think I'd be alone in this.
1. Fritz Leiber's "Fafhrd and the Gray Mouser" series [1].
2. Richard and Wendy Pini's "Elfquest" series [2].
3. Larry Niven's Known Space series [3].
4. Anne McCaffrey's Pern series [4].
As far as I know, no one has even ever started development on #1.
Warner Brothers announced they were going to do an "Elfquest" movie in 2008, but cancelled it because they thought it would compete with another fantasy movie they were doing, "The Hobbit".
One story from #3, "The Soft Weapon" got adapted to the Star Trek universe and became the episode "The Slaver Weapon" of the Star Trek animated series.
#4 almost got to the point of shooting a pilot for a TV series at Warner Broters. They had cast it and sets were being built. But WB requested so many changes in the final script that it was no longer really Pern (I've seen it described as a cross between Xena and Buffy). The showrunner, Ronald D. Moore [5], was a fan of the books and quit rather than going along with the changes, and the project died.
[1] https://en.wikipedia.org/wiki/Fafhrd_and_the_Gray_Mouser
[2] https://en.wikipedia.org/wiki/Elfquest
[3] https://en.wikipedia.org/wiki/Known_Space