Debate fuels my Fire
name those styles of play and settings.
then list how difficult it would be to update them to not be incompatible with modern taste.
then list the setting unique selling points.
Geez, you're demanding huh? The first and last thing you said are essentially the same things.
- Dark Sun: Post-apocalyptic, dark fantasy, sword and sorcery (sandals?), fight against tyranny.
- To update: Add more psionic options, few more racial options. Minimize slavery in society, update things like "boob armor."
I'm not going to go through every setting I think has unique selling points, but I think people here could make good arguments for Planescape, Dragonlance, Spelljammer, Mystara and Birthright (maybe even Greyhawk).