Any kind of zone that's beautiful, has a lot of character, or is otherwise engaging is fine with me. I actually came up with some original ideas (though of course they're mostly not totally original) for an MMO concept I was working on (pause while I look them up)...Ok, I had more than I thought. Altogether they may be somewhat corny and high fantasy, but their meant to supplement a generally realistic environment.
One of the first concepts I played with was use of light, and I ended up with three areas. The first is a prismatic plain, with a highly multicolor environment (blades of grass, drops of rain, lightning bolts, clouds... all different colors). The other is an area completely absent of light-- not a dark area, but a pitch white area, where the mobs are relatively invisible. Finally, an area that operates like a house of mirrors.
Then I just started playing with zones using other matter states and physical elements. e.g., a series of forest catacombs constructed of tree roots, a beach where the sand had all been melted to glass (so a glass beach), an area where the trees burn perpetually (imagine trees with flames where leaves would normally be), an area filled with fungus, a muddy area where it actually rains mud, a giant lilypad area, an area with steeple-like mountains, and a living environment where the area is actually the mob (not an "inside the mob" area).
Those are just some of the ideas I came up with trying to play with visual properties. I didn't do much with sound or other game effects.
Ok, now we're going to get slash fiction of Wint x Kachi somehere... rule 34 and all...
Never confuse your inference as the listener for an implication of the speaker.
Good games are subjective like good food is subjective. You're not going to seriously tell me that there's not a psychological basis for why pizza is great and lutefisk is revolting. The thing about subjectivity is that, as subjects go, humans actually have a great deal in common.