The atmosphere is either Good vs. Evil or Grimdark was my track of thought. Did you mean something like music?
Atmosphere isn't about morality, it's about imposing a particular mood or ambiance on the player, to set the stage in their minds in order to immerse them in the world. Music, writing, art direction etc. all serve whatever mood the game is trying to imprint on you.
Generally speaking, when people like the atmosphere in a game, they like that the game actually *feels* like what it's trying to represent, it's not a function of the morality "systems" the characters operate by.
Exploration is either the Established or Novel Setting.
Exploration is a part of gameplay, and has nothing to with the flavor of the setting. It has to do with the player's traversal of the world and their discovery of its different elements. It's true that exploration can include elements of storytelling, such as finding a legendary sword you've heard about at the end of an option dungeon or something of the sort.
Generally speaking, when people like the exploration in a game they like that the world is rich, full of things to discover (often both in gameplay and story) and they enjoy experiencing and traversing the world the developers have crafted, not simply the setting itself (though exploration can often help legitimise a setting if the world is crafted with care and intent).