A recent article at Gameriot has made a top 10 list of Diablo 3 environments.
The environments that they like are: deserts and wastelands, forests, ancient ruins, and corrupted regions. They didn’t like Hell (Act IV) and think it was done in a hurry with only two waypoints.
I tend to agree - Act IV seems a bit dull compared to the others. However, my list of worst environments is easily topped by the jungles of Kurast! The pygmies were a NIGHTMARE for my Ice Sorceress!