Which cities are comparable with Berlin??
I want to have a discussion here because lots of people say that it can´t be compared with London, Paris, NY, Sydney...
Just say the name of the city, some facts and why it can be compared with Berlin. :)

Comparable is the wrong word. Any city can be "compared" with any other, regardless of differences.

However, what cities are on the same scale or level of Berlin is probably what you are asking.

Of this, there are plenty, and Sydney is certainly one of them. Basically, Berlin can be grouped together with any other city of similar size or slightly larger. Berlin, being a capital city has an added advantage, it also, being split for so many years is a bit "bigger" now that it's joined than many other cities of similar size.

How about comparable with Milan, Rome, Madrid, Barcelona, Sydney, Rio, San Francisco, Toronto, St. Petersburg?

Ha ha ha! Surely not NYC or Paris (which is still closer). But I would say Vienna, Milan, Madrid, Barcelona - this does not include the climate! Or Chicago without the skyscrapers...

If it weren't for Hitler and the Communist takeover of E. Germany, Berlin would likely have overtaken Paris and possibly even London by now. However.......

I'd say Sydney???

Berlin is hard to categorize. Because of a relatively large population it has a sizable economy, but Germans do not perceive Berlin as a top business place. The only multinationals headquartered in Berlin I know of are Shering and Sony Europe, and it is home to some important media companies but that would be about it. Although significantly smaller in population, Frankfurt, Hamburg, Munich, Düsseldorf, Stuttgart are to be seen as the economically dominant cities, but really Germany is a very decentralized country, there is no massive "center of power" like in France or UK, economical and political power is dispersed across the country, although more so in the western half. And Berlin is far from being the richest city in Germany, its local GDP per capita is only about half of the values of the cities mentioned above. The public finances are the worst of all German states excluding Bremen, in fact the city state of Berlin is on the verge of a total financial collapse and will have to be bailed out via a federal rescue package if it is to survive. Fortunately a lot of new life was instilled into the city when it became national capital 15 years ago. While the high hopes of growth didn't materialize as yet, Berlin has changed a lot in all these years and while not the most optimistic place on earth it lost the terribly stagnated feeling it had before.
Had there not been near total destruction in war and decades of communism Berlin might have had a chance to become a top tier city (in fact it was until the war), but then these are nothing but hypothetical musings, the reality is another one. Overall it became a somewhat mediocre city (compared to the top global cities) and for now there is nothing indicating this is going to change anywhere soon. Nonetheless Berlin is a very special and unique place, for my taste the most interesting, varied and the only real city in Germany (ok Hamburg is great too, if in a totally different way).

Thanks for all the good replys. I also thaught which city is on the same level(thank you Justme).
First the populatin of Berlin: 3.4 Mio; with metro 4.2 Mio

Milan: definately not, it´s to small but an economic power
Rome: yes
Madrid: yes, of course
Barcelona: I don´t think they are on the same level
Sydney: yes
Rio: don´t know
San Francisco: yes
Toronto: no, is on an higher level(has a big metro population)
St. Petersburg: hard one, but yes...why not
Vienna: no (lower level)
Chicago: no, has a big metro population and by far more skyscrapers

So maybe a view more maybe from Asia or Africa.
When I´ve find the best I´ll make a poll.

@ DoctorZero, actually Frankfurt is the smaller city by "city proper" council borders, but it has a slightly larger metro population of around 4.9million

@ Berlincity. Milan isn't as small as it seems. The problem is that Italy doesn't use metropolitan area statistics. Milan has approx 8million people in 14,000km²~ surrounding it, which is pretty much the extent of the commuter belt. This compares quite well to the 9million in Chicago's metro extending 20,000km²~, the 4.9million in Frankfurt's Rhein Main that covers 11,000km²~. San Francisco also has a Bay Area (C.M.S.A. metro) exceeding 7.5million.

If anything, Berlin (metro wise) is roughly the same size as Sydney (population) but smaller than Barcelona (4.6m to 5.2m depending on point of view), Madrid (approx 6million), and Vienna is smaller.

In Asia, I guess Berlin can be classified on the same scale as Bijieng and New Delhi, simply because they are low rise cities as compared to the other major cities of their respective countries and all three are political Capitals of their respective countries but still are not the Economic hubs.

In Brazil, I would say it is Porto Alegre, comparing the cityscape and the size of the region.