Personally, present day real world is my least favorite setting for any sort of fiction, though I still play porn games in that setting, if they have the fetishes I like. I didn't know about the limited assets for other settings, but I firmly disagree on real world games being more immersive or easier to relate, as the setting tends to produce superficial and irremarkable character archetypes. My favorite settings would be Steampunk and Post-Apocalypse. Here are two game concepts for either including concept pictures, but these unfortunately looked a lot better on paper than they look on screen.
Shadow of Greatness
Dr. Arieen Byrne has quite a heroic reputation in the City of Coppergate. Only 5 years ago the City's population was almost wiped out by the demon inflicted Great Plague. It was then that Dr. Byrne gathered her band of adventures and set out to rediscover the ancient art of Sorcery and cure the contagion. After the Plague was gone, Dr. Byrne founded the Academy of Arcane Arts and combining Sorcery with modern technology created the first wonders of magitech. Unlike the Wizard Kings of the Lost Age, she didn't claim rulership as God Queen, as she could have, but worked as an advisor to the Coppergate's government, improving life in the city with the help of her newly created artefacts.
However, life wasn't always kind to Dr. Byrne. When she was a small girl, her mother left her and her father becoming a wealthy industrialist's trophy wife. After that time, Arieen heard about her mother only from the yellow press commenting on her fashion choices. When Arieen's father was struck by the plague, she tried to beg her mother to lend her money for medicine, but her mother didn't even talk to her but sent her butler to chase away the girl, dooming her ex-husband in the process. Arieen then vowed to find a care and spare others the fate her father suffered.
Now the mother's husband grew tired of his gold digging wife and sent her packing. But of course the woman still has a daughter with a heroic reputation. So she knocks on Arieen's door begging her daughter to let her life at her mansion. This she does, but only if she works for her as maid. That can't be so bad, can it?
Aside from the obvious mother-daughter bdsm content, this would also kind of the explore the fine line between hero and villain, as the protagonist would be kind of both. Except for the sexual content, which would involve slowly turning her mother into a lesbian submissive, the being a person of public interest protagonist would also have to watch out for people who could notice. Or would they forgive the hero who saved their lives and their city some BDSM sessions with mom anyway?
Warlord's Journey
Jack Caine knew the world only as it had been after the Third World War. His parents sometimes told him about the world before, but even at a young age, he never believed them. A world with heated houses, no mutants or raiders, who would believe that shit after all? His life turned for the worse, when he was 16 and the Rusty Sabres gang of raiders abducted his mother and killed his father. All the while he hid outside, unable to stop the armed attackers. They raped his mother and forced his father to watch (would NOT be visualized in the game, just describing the cruelty of the post-apocalyptic world) before cutting his head off.
Jack vowed to eradicate the Rusty Sabres and joined the mortal enemies, the Bloody Berserkers. He soon rose in their ranks, killing off rival after rival and was praised for his toughness and determination. After a few years he rose to be the gang's leader, drawing a wake of blood through the post-nuclear wasteland. After destroying a couple of settlements he soon found the brothel where the Sabres forced his mother into prostitution. He killed all the members the Rusty Sabres in the most cruel way imaginable and ate their hearts as a warning to any potential sympathizers. And after that realized his mom was still quite hot and now that she had the training as a whore...