None of the zones in the Eastern Kingdoms particularly stand out to me. I chose Hillsbrad Foothills as my favorite because it reminds me most of home with tall lush trees and lakes to the farmland in-between. For these reasons I chose Southshore as Frijona's hometown. Hillsbrad Foothills is also a fairly lore-centric zone, adding to its appeal. Apparently Southshore will be taken over by the Horde in Cataclysm. This is an event that I have not yet determined how Frijona, who has no beef with the Horde, is going to react.
If Hillsbrad Foothills is similar to where I grew up, Feralas is the zone that most resembles the sort of place my family vacationed to when I was a child: huge, lush trees! gorgeous coastline! highborne relics! Okay, perhaps not the relics. Although my dad was really interested in Native American cave paintings. Feralas is, simply, amazingly beautiful. It's easily my favorite realm in all of Azeroth.
I don't know who at Blizzard came up with the idea of giant blue mushrooms in a zone, but it was creative genius! There is no zone I love more than Zangarmarsh. It's breathtaking to explore. The quests are fun. The Sporelings are adorable! Some of the mobs can be herbalized! There's lots of naga to kill!
Picking a favorite zone in Northrend was difficult. I finally decided to go with Zul'Drak because even though it's not the prettiest zone (that would probably be Crystalsong Forest) it has the most interesting quests. I've always found Troll lore incredibly fascinating and Zul'Drak is an entire zone dedicated to it! Zul'Drak is by no means an ugly zone, either. It's unlike any other zone I've seen. It's full of ruins and has a sinister feeling. Stay away from the voodoo!
What are your favorite zones?