I expected to like "Frost/Nixon" better than "Doubt." The reverse happened.
Possibly it was because Frost and Nixon were unappealing characters: self-absorbed schemers. "Doubt" had greater resonance because each of the three main characters was on a journey-- seeking each's greatly different version of the "good."
The priest and the school principal (Philip Seymour Hoffmann and Meryl Streep) were two unrealized halves-- progressive and conservative in battle with each other; each with as many flaws as strengths. The set-up was as if Streep were necessary to keep well-intentioned Hoffmann in balance. Contrary to what one might think, all is not doubt in the movie, for an answer is provided in the character of the third main character, a young nun, Sister James, who is farther along the spiritual path than either of her elders; exhibiting unselfish goodness.
"Frost/Nixon" tells you what to think about the story; a liberal pat answer that Nixon after all was a crook. In asserting this the pure liberals in the plot feel superior. In "Doubt" none of the characters feels pure or superior. The viewer is not told what to think-- but keeps thinking about the movie after leaving the theater.