I'd definitely put Stormreach, perhaps not as a competitor to Sharn, but as a complement.
Sharn exemplifies the Eberron themes of noir, the politics of assorted Houses and other factions, manifest zones etc. Stormreach exhibits the themes of exploration into the unknown, mysterious races with their own agendas, the fallen empires that shaped the setting's history, and the blazing rings of elemental flying ships are often visible over its sky.
If it helps, Stormreach is also the major setting of the Dungeons and Dragons Online MMO.
I don't really know enough to do so, but perhaps some of the FR buffs could give a run-down of what makes Neverwinter and Waterdeep for example, distinctively iconic to the Realms compared to Baldur's gate.
They're being big and famous within the setting, but I'm not sure what criteria that you're using for "iconic".
Waterdeep, Neverwinter, and Baldur's Gate are all very simular because they are all on the sword coast, so they share alot of culture, trade, ect...
Neverwinter and Baldur's Gate are only iconic because of the video games.
http://forgottenrealms.wikia.com/wiki/Waterdeep
Waterdeep is iconic on its own.
Waterdeep is large, its lead by the Open Lord who happens to be a Chosen of Mystra, and Mask Lords whose identity is hidden. It has the Khelban a title of a powerful city wizard named after Khelban Blackstaff a Archwizard and Chosen of Mystra. Depending on edition it has an Elven population larger then most Elven cities at 200,000 Elves and 200,000 Dwarves and its a majority human city (we have two different numbers for citizens of Waterdeep, 2,000,000 and 136,000).
http://forgottenrealms.wikia.com/wiki/Neverwinter
Neverwinter is ruled right now by Lord Nevermber. Its heavily rebuilding. Its cold around Neverwinter, but Neverwinter is magically warm, hence Neverwinter is its name, that is its biggest claim to fame, aside from video games. And its Shadowfell mirror city.
http://forgottenrealms.wikia.com/wiki/Baldur's_Gate
Baldur's Gate's most iconic things are the Flaming Fist Mercanaries, which police and defend the city although they also take other jobs. Plus now they have Little Calim outside the city walls. Oh and Bhaal returned in the city.
That is why I'd replace Neverwinter and Baldur's Gate as Iconic Cities with either Calimport, Skuld, Unthalass, Myth Nentir, Raven's Bluff, Silvermoon, Gloomwrought, Suzail, Alaghon, Rhymanthiin
http://forgottenrealms.wikia.com/wiki/Calimport
Calimport was the largest city in FR until 4e, rivaled only by Waterdeep in size, was founded by a Genie Calim, was ruled by Air Genasi for a time, legendary for its debauchery, kind of a Turkish/arabian nights feel, capital of Calimshan and the former Shoon Empire. Plenty of Tiefling Mercanaries, who were prized for their resistance to fire. A bunch of Gods manifested in the realms in Calimport during the time of troubles, Sharess, Sune, Shar, Ibrunbal, maybe others.
http://forgottenrealms.wikia.com/wiki/Skuld
Skuld is the oldest human city and its where the Mulhorand's Pantheon dwelled, except Sharess (Bast) and Mask (who is concidered a Mulhorand god by adoption, thanks to a Faerun/Mulan exchange program).
Skuld is said to Rival Waterdeep for beauty, but more Egyptian flavoured then Waterdeeps city state. Depending upon editions it could have a larger population too.
A city governed by Pharoh Gods who reside in the city itself.
One of the only cities with a large Aasimar minority population, also a large Tiefling minority, with Half Orcs being the largest none human minority (a side effect of the Orc Gate war).
It was said to have destroyed, its buildings buried in rubble, after the Spellplague, but with the Mulhorand Gods returned and their nation restored its likely been rebuilt like new.
It was the Capital of one of the largest Empires in Faerun history, Mulhorand has encompassed Thay, Morghrom, Semphur, Mulhorand proper, Plains of Purple Dust, Raurin Desert, and Unther at times.
It's likely being rebuilt in 5e.
http://forgottenrealms.wikia.com/wiki/Myth_Nantar
Myth Nantar is a city of Sea Elves, Mermaids, Tritons, Sharlin, regular Elves, and others. Its Mythal allows land dwelling species to breath water, resist cold and pressures among other things. One of my favourite cities in FR.
http://forgottenrealms.wikia.com/wiki/Unthalass
Unthalass was the Capital city of Unther, which is very Canaan/Mesopotamian flavoured, which also used to have a huge Empire consisting of of Unther proper, the southern coastal cities of Algarond, part of the Shaar, Chessenta, Chondath.
Its ruled by Gilgeam (FR Gilgamesh), whose lastest Incarnation fight a war of Libertarian for his people against the Genasi of Shyr (a Abeiran Empire).
He made a deal with the Demon Lord Grazzt for demons.
He is specifically mentioned as a potential Patron for Undying Warlocks, but he also has his priests (he's a God).
Unthalass is being rebuilt after it was destroyed by a fight between Tiamat and Gilgeam, that destroyed both of them (they both came back), then the Sundering.
Once the greatest and most impressive cities in FR, it declined heavily before it was destroyed.
http://forgottenrealms.wikia.com/wiki/Ravens_Bluff
The setting of Living City Campaign of past years. It has the ruins of an ancient Dwarven City and a Drow City (with intact Mythal rare for Drow cities), which draws tourists/adventurers to to it.
http://forgottenrealms.wikia.com/wiki/Silverymoon
The city has a Mythal. The Unicorn Goddess / Archfey makes frequent appearances. One of the Largest places of learning in the realms. Was ruled by a Chosen of Mystra, now ruled by her Son.
http://forgottenrealms.wikia.com/wiki/Gloomwrought
Possibly the last (Shade) Netherese city of any size after their the destruction of their Empire during the Sundering.
Gloomwrought was in the Shadowfell so it would not have been hit by the war and disasters that destroyed most other Shadovar cities.
Its made up of Shadovar humans, Shadar Kai, Dark Ones, Keepers.
It was originally intended to be a Nentir Vale city I think, but RA Salvatore stole it and made it apart of the Shadovar Netherese Empire. Drizzt has been there.
http://forgottenrealms.wikia.com/wiki/Suzail
The Capital of one of the few actual Kingdoms of FR, Cormyr. (Off the top of my head Tethyr, Cormyr, Hartvale, are the only traditional Monarchy style Kingdoms, Oligioachies, City States, Magocracies, and Theocracies are more common in FR.).
War Wizards, Purple Dragon Nights, super iconic.
http://forgottenrealms.wikia.com/wiki/Alaghôn
Alaghôn
Alaghôn is the Capital of Turmish, the only none city state democracy in FR.
It was in decline after the Spellplague thanks to it causing the city to become land locked, but the Sundering made it a port again, bringing back trade and wealth to the city.
It the home city of the Assembly of Stars, the parliament of Turmish, and the head quarters of the Emerald Enclave, the far reaching organization of Druids, Rangers, and other nature and balance loving people.
http://forgottenrealms.wikia.com/wiki/Faer'tel'miir
Rhymanthiin is a Elven/Sharn city in the High Moor.
It was created by a spell of high magic. Its made partly of the Sharn who can appear from the walls and streets.
Its called the City of Hope and if you have ill intentions you can't even find the city.
It has its own copy of Black Staff tower, the eight tower, so its has simularities to Waterdeep, but nicer and Elvish and black building materials.
