Heat was Michael Mann's best work by far. De Niro and Pacino were fine in it, but not even close to work in their much younger years. The only work since 1980 I have loved with Pacino was Donnie Brasco. He was fantastic, but also liked him in Angels in America. Otherwise he's been on autopilot. Obviously you have Serpico, dog day's afternoon, the unforgettable over the top scarface, carlitos way, and godfathers.
De Niro was surprisingly good in the Joker and Silver linings playbook. Otherwise he has some absolute monolith-level performances in taxi driver, Raging Bull, Kings of Comedy, and deerhunter. Fantastic in Casino, mean streets, Jackie Brown, once upon a time in America, goodfellas.
Their performances in Heat were cool in the sense of them sharing a scene together for the first time. Other than that, it was all Michael Mann.