This guy I am involved says he would put his daughter before a relationship. I don't think that's how it should be.
The quality of girls relationship with her father will affect how she is with men for the rest of her life- you on the other hand are an adult and should be able to accept decisions/behaviors more rationally.
Its completely understandable he would put her "first" but rather than thinking of it that way it needs to be presented as being able to balance his relationship with you with the one he has with his daughter.
Be wary if he's being over protective of her but also try and consider it from his viewpoint- would you let a man come before your son?