I think Gotham appeals to more audience than the usual comic book series (Daredevil, Arrrow, Flash, SHIELDS, etc.).
For example, my wife absolutely hates all the comic book movies (she hated Batman vs Superman) and TV series (even Daredevil), but she loves Gotham, even though she knows all the characters are comic book.
I think Gotham is fantastic. It's mature, but still has natural humor (not forced like most shows). It doesn't show any graphic violence, but it does imply it (as a necessary evil).