Young Pacino (Panic in Needle Park, Godfather,Godfather 2, Dog Day Afternoon, …And Justice for All, Cruising) is better than young De Niro (Mean Streets, Godfather 2, Taxi Driver, Raging Bull, The Deer Hunter, King of Comedy), though De Niro clearly made better movies…The movies were not better for De Niro necessarily, though. He worked with better directors than Pacino.
Old Pacino (Dick Tracy, Glengarry Glenn Ross, Scent of a Woman) is definitely not as good as Old Deniro (Awakenings, Cape Fear, Goodfellas, Casino).
Present day: They both suck. Righteous Kill was horrible but Pacino was better than De Niro in it for sure.
Neither of them are as good as Marlon Brando.