Size and freedom sum it up pretty nicely =P
We’ve built First Person Shooter (FPS) engines from the rooms outs.. From mazes with much the same way in as the same way out as the previous “area”, at the end of the map.
Now we play much the same still. Except, taking Quake Wars (ETQW) for example, were playing in more of an “outdoor” maze.. Morrowind was of awe, not just because of its size and scale, but also because of the “ALMOST” seemingly alive world of moons and stars and clouds and storms helped make it pretty well too.. But for the most part, Morrowind was a big “disc” on the outside.. Mazey and indoors like, on the inside.
Oblivion Was much the same, actually more like a blob that looks like Australia, and on the boundarys of invisible walls (OUCH!) a “seemingly” endless vista of more.. Trees and stuff.
I like Orbiter, because it is a planet! A ball! You can just go around and around, or up and away.