If you want an open world game with truly satisfying exploration and depth to the world, your options are basically Ultima 7, and Gothic 1 & 2. Some of this is down to game and loot mechanics, but it's also just down to effort spent on creating detail in thew world. We're unlikely to ever see a game world so fully realized again, as devs have universally decided to go for breadth over depth because it apparently takes too much effort to do otherwise. W3's gameworld was aesthetically well designed, but in gameplay terms little would have been lost if they just had you teleport between points of interest (which they sort of did, ultimately...).