[Eomer of the Rohirrim]

I think he is far less complex. He is the action hero of the film, who saves the day and gets the girl.

But you are right to point out the lack of screentime needed to even vaguely get across the subtleties of Book-Gorn. Movie-Gorn was portrayed well, I thought, definitely within the context of the film. However, I do think that he (necessarily) came across as rather simplified and consequently not so interesting.