What an excellent question! I am just about to start teaching this novel to my seniors and hadn't thought of comparing it to this wonderful film. You are right in indicating that both of these texts explore, albeit in different ways, what it means to be human and how we define humanity.
Let me start by talking about Bladerunner. We are presented with a dystopian world that is over-polluted and where anyone who is healthy enough has left for the colonies. The strange collection of misfits that are left include bladerunners, who are special police officers charged with making sure that no replicants (androids who resemble humans in every sense) make it to earth. If they do find any replicants, they are to "retire" or kill them. However, the film explores what constitutes a human by presenting us with replicants, like Rachel, who have been given human memories. How does that make her differ from a human? The film asks some very hard questions about what distinguishes us as humans from other species and whether we are actually as unique as we think we are.
Likewise, in Frankenstein, similar questions are raised. Victor Frankenstein "makes" his "creature," that is almost always referred to a "monster." Yet this is a label that the "monster" himself does his best to reject and to shrug off. In some ways, he shows an understanding of humanity and life that supercedes those around him. Shelley seems to contrast the bloodthirsty nature of the crowd at Justine's trial to the monster to problematise the whole concept of humanity. The monster starts off humane--it is only the inhumanity of man that makes him inhumane.