I think that might be what makes 'urban fantasy romantic lead' different from 'all other books romantic lead'. Urban fantasy is a genre where it is pretty much expected that the romance will take several books. Ilona Andrews is my favorite example-- the Kate Daniels books are urban fantasy and the Edge books are paranormal romance.

I'd say that for an urban fantasy in specific, the romantic lead has to change over the course of the story. He (usually he) can start out adversarial and condescending, and he'll just about always start out stronger on at least one axis, but he has to change in a meaningful way by the time the romance gets going.