Whether something is alternative or not is in the eye of the beholder.Usually, the alternative quarter of a city is where the nightlife is, where artists and the "in-crowd"live.
For me, the part of Berlin around Alexanderplatz, Kreuzberg and Mitte is the "normal" Berlin. The part where I spend most of my time, where "it happens". Therefore, my "alternative Berlin" is the western sections, like Dahlem, Grunewald and Schlachtensee where the well-off-people live. One might argue if they are the happy crowd, but they sure have some beautiful architecture! It's a part of Berlin most tourists never go to- about 15 miles off Alexanderplatz