Fallout 1&2.
These games are classic, and without GOG, basically relics of the past. The isometric turn-based gameplay would be perfect for a mobile port. It would be great to add new assets and content. It would be quite fun to design sprites in the 90’s style the games have.
I’d be happy if Bethesda made a mobile edition, assuming they had the publishing rights to it. I’d pay whatever the going rate for a good mobile game is now adays (without micro transaction).
The trademark of Fallout is probably too valuable for anyone to be able to get away with making a ground-up port to a modern system in an open source fashion.