Frankly, Berlin has some EXCEPTIONAL hotels at great prices:

Rocco Forte (eaten there, looks a bit dark to me but is well regarded!)
Soho House (which is meant to be very, very good)
Grand Hyatt (stayed there, modern, very good)
Ritz-Carlton (stayed there, classic, very good)
etc etc

Plus plenty of 2nd tier properties which would still be better than the best hotel in many EU cities - Adlon, Regent, Westin Grand etc

In fact, there are few cities in Europe which offer a better selection, and none which offer such a good selection at such low prices.