Game world

For me it's the graphics engine, which creates an atmosphere. Similar in Diablo 2, just something about the atmosphere there. Not saying they have a similar atmosphere, but that they are similar in that they both have an atmosphere that appeals to me. They each have in my opinion very unique graphics. Consider the view when you are walking over a bridge in Dungeon Siege, it has extreme depth to it, something that makes the world feel more alive than other worlds. I kinda feel I am there. Now with Diablo 2, it's like it's all hand-drawn, somehow.
----
----
----