They've been in three movies together: The Godfather Part II, Heat, and most recently Righteous Kill. They didn't share any screen time in Godfather, had a memorable "face-off" in Heat, and had much more of a collaborative experience in Righteous Kill. Of course, Godfather II>Heat>Righteous Kill.
Round 1, FIGHT!
I like more of Al Pacino's roles and his acting, just my opinion. I liked that movie they did together, forgot the name unfortunately..