I really like environments that are centered around vegetation, green tones, and forests. I also like environments centered around deserts and mountains. Stuff like that appears much in Prince of Persia Sands of Time, and Legend of Mana; two of my favorite games. And it's also the reason why Tanaris, Un'Goro Crater, Stranglethorn Vale, Elwyn Forest, Feralis, and Silithis are my favorite areas in WoW.
I also really like the "clean tech" look that the Protoss have in both the original and new Starcraft game. Also the "bio tech" concept that the Zerg have I like as well.