Some attributes to ponder and develop:
Society building in multiplayer: players build and develop societies and organizations together which service and threaten other players'' societies and organizations. Players define the structure, hierarchy, rules, and laws of their organizations.
Multi-agent (NPC) communication and cooperation: Requires knowledge and how to use knowledge.
Random goal generation with random side-plots and sub-plots added to remove the template feel of the goals.
An AI game-moderator which may override and prevent unlucky events (like character death) if this is going to do nothing for the player''s enjoyment of the game. In other words, there are certain types of games where immersion and experience are more important than strictly testing the player''s ability to advance.
Detailed health and medical modeling of the character without boring the player with the details. In other words, a player may die of bleeding to death or severe head trauma.
Some possible scenarios that I believe should see more exposure include: (note these need not be cast within any game framework)
Alternative realities / alternative worlds. (sci-fi, but with little emphasis on space or high-tech)
Wild West: horses, guns, trains, outlaws, wanted posters, etc.
Forensic medicine: crime scene investigation, criminal profiling, etc.
Medical thrillers: Probing sinister medical plots, exposing patient testing, etc.
Technical thrillers: Genetic engineering, viruses, DNA manipulation, etc.
Hacking: Either networks, or highrise buildings, information attainment, extraction, etc.
Intrigue: Espionage, spying, intelligence operations, etc.
Political: Power hierarchies, organizations, etc. (see the first paragraph of this post).