Kölsch (Cologne) and Alt (Düsseldorf) is not just regionality, but it's a neighborhood feud. I've seen some bars offer the other city's beer, and ask a ridiculously high price. And naturally, there are plenty of jokes of how the other city's beer is supposedly produced, where most involve urinating.
A really good Helles or German Pils is a treat, and amongst the many breweries I've tried in the US, I have not anything that came close to an Augustiner Helles or Rothaus Pils (which doesn't mean it doesn't exist, it just means I haven't had it). But then again, Augustiner or Rothaus is the exception here in Germany and not the rule, unless you happen to be in Munich or the Black Forest. Unfortunately, you will get served skunked Beck's (green bottles) in many places and for some, the skunky smell is part of the Pilsener experience.