Our tradional view of this genre is that of GTA, Skyrim or ore recently Dying Light. These are massive maps, freely explorable and rich in content. However they share the same design issue, which is the requirement to keep the player on the story arc.
This is generally achieved in a variation of the same method which is a dot on map objective approach. Go from A to B, Do X and Y, return to A again. While the worlds are open the game is in fact linear!!
Where the Souls series differs is that although I would say the world itself while freely explorable is not quite as open as the aforementioned titles, the game itself is far more open.
You start the game vulnerable....physically but also mentally because of the lack of information. The lack of an objective, not being told what to do or where to go is unnerving but also forces true exploration. I have to choose between 4 paths to take but there is nobody to tell which is the right one. Only exploration of these paths will increase my knowledge.
I hope this design approach could be adopted some day for a GTA esque game.