Basically, all state universities have a good level of teaching, it doesn't matter where you go on the undergrad level. Later, your field is important; universities have different specializations. Some people prefer smaller universities (more intimate teaching), others bigger universities (more different lectures - more choice). If you only know English, it limits your choices of course.
So start with the subject you want to study, or with the kind of city you want to live in. Do you want to live in a big city or a small city? Do you prefer a big university?
What's your level - do you need general teaching or do you want to get into specialities? In the first case, any university that offers the course is fine, in the second, look closer.
As far as I know, all universities in Germany are more or less equivalent. In Germany no one will ask what university you went to, when you apply for a job. Unless it's an applied university (Fachhochschuhle).
With that in mind, I would recommend you to choose your mayor first and then figure out which university has English speaking programs for that mayor. In Germany you have to choose your mayor before you apply to University.
