The world generator is powerful and is getting better with every release. It produces amazing worlds with rich geography and history.
No matter how sophisticated the world is, when I enter the game either in Adventure or in Fortress mode, it soon looses it's character and becomes yet another generated world.
Yes, the landscape looks as real as you tweak the parameters. Yes, there is a history, people have their relatives and describe places and events. Regions have their name. It is all in, yet it still does not help me "live in" such a world.
I don't ask for more features - I suggest more "insight" into the features that are already in.
Adventure mode tweaks:
1) The books or slabs (or engravings) in the castles could contain family trees. Family trees could also be viewed in Legends mode.
2) When asked about family, people should not give away random fact about their relatives but should start a narrative - I am, my wife is, my children are, my parents are, they came from, my grandparents … as long as you press "next" the story continues going deeper and deeper in the family tree.
3) Lords/Ladies or other rulers (or one of their subjects in their residence) could offer the talk about the history of their realm, about their enemies, about battles they fought.
4) Towns should have some statues displaying people or events from their past.
5) The adventurer map (Q) could contain much more features: history of adventurers moves, events, familiar people. It could be exported into graphical file with some elementary icons and routes.
Fortress mode tweaks:
1) The embark scenario may differ upon where you decide to go: if you start within dwarven realm, you may be given more points or dwarfs to start but you already start with some noble supervisor. If you embark in human/elven/goblin/kobold/different realm, there might be some demands made by diplomats: practical or even gruesome for goblins or kobolds, practical or "ideological" for hums/elves - depending upon the ruler. If you start in the wild, you're on your own - less resources in the beginning, it might take longer before first caravans drop in, but you start as your own lord.
2) Families should stick together. Relatives could be unhappy when their members live away from each other - they might demand "flats" with different rooms. There should be loners who hate the rest of their families and demand separation as well :-)
3) There should be a historian noble/administrator, who would write down the history of your fortress. When engraving or forging some historical event, the maker should come and consult historian. Historian should track combat kills for all the dwarves (aggregated kills).
Legends mode tweaks:
The legends mode already gives you some basic maps (that can be layered into pretty decent map using external graphical editors), historical maps and hacker's view into the history, artifacts and others features.
1) The generated (graphical) maps could be generated with borders of the realms, the capitals and cities identified, even with the names put in.
2) Legends mode could also generate sort of "hypertext/html" map, i.e. graphical map with generated map regions linked to additional text info. Such a map might be updated during adventure mode.
3) Listed events, entities, artifacts should be displayable in (ascii-based) map (during legends mode) and might be added into list that gets exported in graphical map.