All major German cities have at least one good hotel. Berlin and Munich are probably the 2 best places for vacation (in terms of interesting touring sites) and happen to have the cream of the city luxury hotels. Otherwise there are some stunning castle hotels, mostly in the Rhine valley. A different kind of luxury at times. Or go to Vienna (much better hotels and restaurants for the price). Imperial hotel in Wien is one of the 10 best hotels in the world by most measures (while Germany has none).