The Honor Harrington series. Would have to be 3d animated IMHO- One major component of the books is humans have received lifespan extension treatments which greatly slows down human aging. So you would need a ton of 18 to 25 year-old actors who can pull off playing 50 and 100-year-old characters.

Philip Jose Farmer's Riverworld series could be a fun series/world to adapt to a series, but also infuriating if they cut it short after two seasons.

The Scholomance series by Naomi Novak could be great.

Would love to see an Otherland adaptation into a series. There was a film being planned but haven’t heard anything in a while. Tad Williams is a fantastic author.

The Hyperion books by Dan Simmons.

Something by Alastair Reynolds. I think Eversion would work as a mini series. Otherwise Revelation Space would be sick, but perhaps as an animated show instead of live-action.

Melanie Rawn: The Dragon Prince

I didn't think special effects could do it justice in the past, but I think they've definitely advanced far enough now.

Leviathan by Scott Westerfeld. You'd need a massive budget to make the darwinists look convincing though so it'll probably never happen.

I know it had a brief go in the 90s, but I’d love to see a proper adaptation of Animorphs. Those books were wild, especially for something I remember starting in 3rd or 4th grade. I’d prefer animated personally, but I would tolerate another live action series. Tech has definitely improved enough to do the alien races justice in either format. Another pick would be Vampire Hunter D. It got a couple anime movies but I think a series could really do it some justice. It has such a fascinating world.

A Darker Shade of Magic was slated for a movie, then a TV show, but I think it's basically been dropped. I really enjoyed that series and think it would be a pretty easy adaptation.

Tad Williams - The Dragonbone Chair

Trudi Canavan - The Black Magician Trilogy