What US cities are good to live in when relying on public transportation?

I moved to Chicago last year and sold my car because it was absolutely unnecessary at the time. My boyfriend bought a manual shortly after that I don't know how to drive (of course). In a few short months we will be leaving Chicago for another city, and I need good public transportation. I have done a lot of research, but still managed to be duped by thinking the city we wanted to go to had useful public trans (Charleston, SC). Although I'm sure Chicago has one of the best systems out there, does anyone know of other good cities with public trans that is actually worth using? Thank you :)