Dune. Though I imagine there will be more efforts in coming years.

Basicly every anime that isn't Dragon Ball, they generally only get half-hearted fighting games. A lot of them could make for great RPG settings. I've also thought a lot about the idea of a Death Note visual novel which a different Kira and detective where you can play from both perspectives.

Also give me a nonsense adventure game based on The Hitchhiker's Guide to the Galaxy please.

Avatar: The Last Airbender is one of the most-loved TV shows of all-time. The Legend of Korra is liked, and the spin-off novels are liked as well.
No video game has done the IP justice to date. Even The Legend of Korra get a mixed response, and it's probably the best-reviewed Avatar game on console or PC.
You need either passionate and skilled indie devs or huge devs to do the IP justice in fighting games, RPGs, etc. So far, Nickelodeon has not chosen either.
A game in The World of Avatar like Skyrim or Tears of the Kingdom could be not just a great game, but an all-time great. Heck, an indie non-open world RPG (even turn-based for a classic feel) could be loads of fun.

Can't fix something that was already perfect.  The rogue series was great.  Factor 5 is missed.

Discworld Series:
Discwold has plenty of different regions, cultures and characters. Plenty of opportunities here for different genre of games with different characters all having the typically humor and wackiness.

I mentioned Macross.

Ghost in the Shell. We live in an era where Cyberpunk games are a dime a dozen. Ghost in the Shell would make a great Action/Adventure game about solving crimes and third-person action.

Bubblegum Crisis. How is there not a third-person shooter? It's time!

The Last Starfighter. Not hard to imagine what this could be.

BERSERK! 3 games exist. One Japan only. One is a mediocre Warriors game. The other is a clunky Dreamcast game (I like it tho). We need a good-sized budget Berserk game in the Black Swordsman arc or later. I truly want Capcom to make it with Itsuno.  It's not a clone of DMC but def an action game. Soulstice may be as close as I ever get.

Futurama and The Simpsons both could use RPGs.

Honestly, though, I still have an overall jaundiced view on outside licenses. The Ninja Turtles games and The Simpsons Arcade Game were fun. That's about the limit of my tolerance for licenses. 

Star Trek never had any really good video games. Instead, games like Starflight and No Man's Sky captured the spirit of Star Trek without being encumbered by a license.  Ditto with Aliens. There have been some decent Alien games, but Metroid did a far better job of conveying the spirit of Alien in video game form than any actual Alien game ever did or likely will.  We have a whole body of RPGs out there that didn't need the Tolkien estate's permission to make them awesome. 

Atari attempted twice to do a TLS game. The first attempt became Solaris on the 2600. The second attempt was reworked into Star Raiders II on the Atari 8-bit line. However, a prototype of TLS was leaked out in the 1980s. I've played it. 

I think Avatar: The Last Airbender is an easy answer. Pick your avatar (in design, where they start out/what element they start out with, personality traits, etc). The game makes the element that is opposite your personality the "hardest" part of the game, but it's open world. Finding avatar shrines is how you unlock new moves for your elements, and leveling up is how you can spend points on learning moves. Puzzles based on elements that you have, which means sometimes backtracking once you unlock others. Idk, it all seems so simple that I can't believe it hasn't been done before.

Outside of that franchise, I think The Matrix is a good one. Path of Neo was fun and the Unreal Engine demo was interesting...but nothing that really wowed me gameplay wise. I think Fast and Furious could make for an interesting game, given how farfetched and over the top the series is.

Last one would be the Stargate franchise. I think that one could work really well in the modern day and age. Multiple universes/planets to explore, alien creatures, lots of different weapons, varied environments, and there is a boatload of story content that can be used. But I'm biased towards this franchise so....

Am I in the minority in thinking that Avatar:TAL/Korea would be a terrible game? Just thinking how complex the controls would have to be to account for 4 elements + the spiritual powers the character has? He'll people were complaining about ToTK controls and that would look like a Mario 1 compared to the hypothetical Avatar game.