Do you mean books in which the heroine haughtily thinks she's too good for the hero, or ones in which the hero himself thinks he's not worthy of the heroine?
The latter situation occurs in many romances, both historical and contemporary--e.g., the hero returns from war wounded in mind and/or body and feels unworthy of love, or he's a self-made man and she's one of the privileged elite. Some examples
here.
For the former, Goodreads has a "
heroine spoiled" shelf, which might fit your search.