The point we're trying to make is, Nolan made a good and well respected Batman film with an unknown main villain. Point being, it can be done.The general audience didn't know who he was, but it doesn't change his importance as a character. Ra's Al Ghul is one of Batman's biggest foes, whether the general audience knew about him or not. The only reason Penguin & Riddler were more recognizable was because of the 60s TV Show. It doesn't make them more dangerous or important than Ra's.
They didn't know who Two-Face was before Batman Forever either. Does that make him a minor villain?