I'm with Kesil on this one, it's good to focus on the main aspect of the drawing, which is the girl getting her dick and her physical reaction to it. It's also okay to use the generic bald male design to simulate the man being anbiguious so anyone can be in thier shoes, but the fact you did enough work on the males to actaully give definition and facial expressions make me feel like thier are a half-finished product of the drawing and you kind of gave up on them to finish the picture.
The work is great, but the males kind of detract because they are too middle ground. Not ambiguious enough nor are they a fully finished character like the girls are. I wont tell you to change them becausse I am only giving my take on they way it seems, it's still great art, it just feels like something is slightly lacking in the finished product.