What's your favorite high level zone, from any expansion, not a raid. Examples include Eastern Plaguelands, Netherstorm, Shadowmoon Valley, Storm Peaks, Icecrown, Twilight Highlands, Dread Wastes, and Vail of Eternal Blossems. (I'm sure I'm missing several from Vanilla, just has been so long, I forgot what the original high level zones were).
Personally I'm partial to Storm Peaks. I loved the titan lore, and the zone was just gorgeous to me.
I really enjoyed Icecrown Glacier. It gave you a ton of blues that prepped you for heroics almost right out of the gate, and many of it's quests were really good (the entire Matthis Lehrner chain is still my favorite quest chain in the game.)
Then again I'm also partial to Netherstorm and Dread Wastes.
Sadly my favorite questing zones, those of Cata, had a very weak endzone, and Dread Wastes is pretty unbearable, as much as I love Pandaria. Gotta give this to Storm Peaks, it had a pretty cool atmosphere, and for once the snowy landscape of Northrend actually looked great. Plus, Yogg-Saron's shadow looming over the place made it feel very threatening.
To be honest, I can't think of any of the high level zones that I really liked. All were pretty cool, but none really stood out as "uber awesome". My favorite zones were usually lower level. Probably because I generally stopped questing once I hit max level, so I never really spent much time in high level zones. /shrug
Certainly Silithus if nothing more than for nostalgia reasons. I was so used to the bright, sunny desert of Tanaris that the dark sands of Silithus were super cool to me. Of course, there were like literally 9 quests in that entire zone but I was so antsy to get to 58 back during BC that I grinded mobs for hours.