Star Wars: Galaxies had a killer open world housing system! I loved it and nothing else I've played has even come close to what SW:G had. Plus, after a bit of patching they included a system where you can create a city that shows up on the map, including shuttle/fast travel points and benefits to locals. Housing wasn't instanced, so you could build nearly anywhere on the map outside of in-game cities and other players cities. It was truly awesome. Sony Online Entertainment screwed it over again and again and again, and now it's gone. I played that game for years.
Never played UO but I heard good things.
Highly recommend this game. It got better once they started allowing you to quicksave and checkpoint your progress at towns/outposts. Prepare to die. A lot. Live and drink, friend.