> Unraveling the story behind the stereotype of video games being for boys.

This tells you that there exists a stereotype. This stereotype suggests that video games are for boys. It also suggests that an unravelling is intended, i.e. a disentanglement of multiple connected strands related to the persistence of a stereotype. Furthermore, calling something a stereotype outside psychological research suggests that something is regarded as "a preconceived and oversimplified idea of the characteristics which typify a person, situation, etc." (as defined by the OED).

This suggests a thesis that

a) disagrees with the premise that video games are, indeed, only for boys

b) will try to portray how this stereotype came into existence, i.e. it will try to trace its genesis.