Dalaran

Wait, did Dalaran just bubble-hearth?

To get to Dalaran:

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• Mages can learn to teleport to Dalaran after completing the short Dragonblight quest Attunement to Dalaran (Alliance / Horde) available at level 71.
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• Mages can learn to open a portal to Dalaran at level 74. Warlocks can also summon players to Dalaran.
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• Anyone who has reached level 74 can pick up the quest The Magical Kingdom of Dalaran (Alliance / Horde / Neutral) from any of several members of the Kirin Tor. This quest will offer a one-time teleport to Dalaran.
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• Once a player has arrived in Dalaran, they can complete the quest Learning to Leave and Return: the Magical Way to allow them future access to Dalaran by using the teleport crystal below the city. The quest requires level 68.
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• Several level 80 rings that teleport the player to Dalaran are available for 8500g each.
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• Any player who has learned Cold Weather Flying may fly themselves to Dalaran. Cold Weather Flying requires level 68 and costs 500g.
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Orgrimmar and Thunder Bluff are about as close to legendary horde cities you are going to get.

In WC2, orcs came over through the dark portal and were defeated and forced into servitude to humans. Anything they built on Azeroth was destroyed, and most of it was temporary. After Thrall escaped, he built small outposts until he migrated to Kalimdor and built Orgrimmar. He brought the trolls, who have cities (ZA, ZG) but almost every other troll in WoW is hostile to horde trolls because they think of the orcs as weak (because they were defeated). So horde trolls have no place to call home except the horde.

Tauren were driven out of the Barrens by Centaur, and up until Carine reunited the tribes into a single entity they lived nomad on the plains. They never established a legit city until Thunder Bluff.

In addition, all except the northern reaches of Kalimdor were desolate until the horde came over. Night Elves were the only ones to live there, and they mostly slept and stayed in peace with nature, so expansion was not a top concern considering they were immortal.

Meanwhile, dwarves and humans lived on Azeroth (the continent) for the entire history of warcraft, established numerous kingdoms and didnt have their whole planet destroyed (Draenor). So while the humans and dwarves built cities like Ironforge and Stormwind, Dalaran, Lorderon, the horde were still in Outland before Guldan destroyed it, and even then they were in constant war with Draenei, demons and such.

Humans have so many cities because they went the whole time leading up to Medivh opening the dark portal in complete peace for the most part. (They emerged after the sundering, so they probably had no conflict with elves and had peaceful relations with Silvermoon).

Also, the forsaken only originated in the last 15 years of warcraft history, since Sylvannas broke out of Nerzuls control and raided Lorderon and built UC. Maybe Sylvannas will take over Icecrown when the Lich King ether dies or escapes Azeroth, and turns Northrend into a forsaken empire. Considering they made UC is such a short time.