I am confused. Is this a general discussion on gender equality or is this a discussion on gender equality as portrayed by 50 Shades?
If the latter, I think an important point which has not been mentioned is the dynamics of a S&M relationship. In such a relationship, there is a dominant figure and a subservient figure. It may appear that the dom is more 'superior' than the sub, but the ultimate power lies in the sub (via safewords or simply willingness to participate). Some people's desires are to be dominated, and the mentality of the dom is to satiate the sub's desires (contrary to the popular belief that is to objectify the sub). So in reality, it's an unconventional relationship that is nevertheless still healthy.
In some ways, even 50 Shades does not portray this dynamics in its full subtlety. However, the existence of S&M relationships is not evidence for gender inequality, it comes down to a matter of personal desires.