Been to Berlin a zillion of times, mostly on transit to poland though, which always is something like central station -> s-bahn -> Quick check, TV
-tower still there? good! -> hipster leave me alone, bloody moron -> Lichtenberg station -> Hell outta there! So that doesn't really count...
*Visited* Berlin maybe 3 1/2 times, and even though I like it as a city and I love the locals, it's just not my cup of tea.
Too loud, to wild, to hip for my taste and I'd consider myself everything but a boring person
Opposed to that I've been to
Copenhagen ~ 20 times
Warsaw ~ 15 times, but a bit like Berlin, mostly transit, but often with overnight stay. I still prefer Krakow and Gdansk over Wwa
Vienna ~ 15 times
London ~ 10 times
Additionally I've properly visited Oslo, Stockholm, Riga and Belgrade more often than Berlin, plus a dozen of visits to Barcelona and Zurich which, of course, aren't capitals so don't qualify