Al Pacino was untouchable in the 70s. Panic in Needle Park, both Godfathers (II especially), Dog Day Afternoon, Serpico, ...And Justice For All. In a decade of many great performances (Hoffman with Kramer vs. Kramer and All the President's Men, Nicholson with Chinatown and One Flew Over the ****oo's Nest, John Cazale in Godfather II and the Deer Hunter, De Niro with Godfather II and Taxi Driver, just to name a FEW of the great acting performances of the decade), Pacino was consistent in his method.
That Brando would be nominated for Best Actor in Godfather I is understandable (though I wonder how someone can watch the film and determine that Vito is the lead male character, not Michael), but losing the award to Art Carney is an embarrassment. Often the Academy attempts to reward actors later in their career for roles that are strong but not what they are best known for, which is the case with Pacino and Scent of a Woman, but it's impossible to live down that kind of shame. Who today remembers Carney in Harry and Tonto the way people idolize Pacino's portrayal of Michael?
In any case, after all that ranting I would nominate Godfather II and Serpico as Al Pacino's best roles of that decade.
EDIT: Morgan Freeman in The Shawshank Redemption always impresses me whenever I watch it.