I wouldn't say so, considering not only does it not live up to Theoden's speech in the books, but also have to compete with the other scenes of a movie that has some of the best high points in cinema such as most of Samwise's lines, the charge on the Black Gate, the "You Bow to No One" scene and the ending. Then again, I wouldn't argue against a LotR scene that's not top tier still being amongst the high tier of cinema in general, and as far as inspirational speeches and charges against an enemy goes, this is one of the best (though Aragorn's "I bid you stand, men of the west!" speech still beats it).