With the risk of being discarded as nonconstructive and trolling and god knows what... I have to say: this thread is full of bull.
If something gets my hairs up straight, it's (among other things) "what's the most important X in history"?
There is one simple answer: different times, different regions.
As Ushgarak pointed out on page 1: Rome? People think of the Roman Empire, not Rome when referring to it. London? Much more needed in the empire than Rome. Is it there for more important? No. Why? Because it's different times.
On this page for example: "America has the biggest communication network". So? Communication is not everything. Besides, with such arguments there can't be a "most important city in history" (or region in this case) because in 50 years another region will have a bigger and better communication network.
You simply can't pick, because saying for instance the Dutch in Asia were important for trade is doing incredible injustice to the Silk Roads.
Another thing is: what about the cities you forget? I highly doubt anyone knows the Belgian city of Mechelen, but for the Austrian Hapsburgers it was very important. I don't remember if it was their capital of the Low Countries, but they certainly saw it as an important city. (Last year some descendant got married in the cathedral of Mechelen... kinda significant he picked Mechelen instead of Vienna, no?).
Besides, you're also asking to discuss taste. What's holding someone to say (s)he thinks Cuzco was the most important city in history due to the city being shaped like a leopard? What's holding someone else to say that Troy was the most important city in history (just let's say it did exist where most claim it has been) because of the famous war?
There has been made a list of most popular American presidents public today (or yesterday?)... Lincoln got first because he united the States after ending the civil war. Great! Good job! But why didn't Roosevelt win? Was he less important? Of course not! But again: different times. I find it appalling that historians dare to venture into "who's more important". Bush junior was somewhere at the end, thus with the least popular... how can historians judge him? If they should know something, it's that things can change easily: in perhaps 20 years, he might actually be one of the most popular ones.
Again, you simply can't compare. It's down to taste and what you can remember at the point the question is asked. But most important: you're doing injustice to history by comparing across borders and time and therefore reducing certain events while praising others.