With riveting performances not seen since “The Godfather” (or at least “L. A. Confidential,” the story opens in Boston’s “Southie” circa 1975, on little Colin Sullivan, the only kid that Irish mobster Frank Costello (Jack Nicholson) is nice to.  That’s until he grows up to be Matt Damon, a police officer rising rapidly in the ranks. Nicholson’s mantra is if you’re at the end of pistol, it doesn’t matter if you’re a cop or a killer, though he finds uses for Damon, as a cop. Enter Billy Costigan (Leonardo DiCaprio) a fellow police officer and a good guy with a long history of naughty uncles, immediately sent undercover by superior officers (Mark Wahlberg and Martin Sheen) to infiltrate Costello’s murders and nail him for good.  Suddenly the movie becomes good guy (DiCaprio) behaving badly, and bad guy (Damon) behaving good. Director Martin Scorsese is back in full force completely making this a DiCaprio showpiece. It’s clear early-on that DiCaprio, now in his third Scorsese film, is this generation’s DeNiro.  Bostonians will love the inside humor coupled with blood, sacrifice and lies.  And the dropped “r” accents are right-on, since both Damon and Wahlberg are natives. If only I could give more than – four tiaras.