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).