As has been noted above, there are a remarkable number of good
characters/portrayals in the movies. While Gandalf and Boromir (among others)are well acted and the casting by PJ and friends was good I'd say Eowyn, partly because I had significant doubts that the character could be adequately portrayed in the movies.
The worst must again be mentioned, Denethor!
While not depicted in the book as kindly (ala Theoden) I see him as more
a tragic hero, flawed but dedicated to Gondor, and to some extent, the West as a whole. Although in one of his Letters JRRT takes a surprisingly negative view
of Denethor. His movie bits were awful not just as a one-dimentional "crazy"
but for the ridiculous Gandalf/Denethor interactions.
