WILSON WEBB/WARNER BROS. PICTURES

It’s almost like every popular movie about crooks and cops made in the last four decades, but never enough like its own movie. An extended gunfight mimics the famous train-station staircase shootout in “The Untouchables.” But mimic is all it does. A lot of people who’ll see “Gangster Squad” will also have seen “The Untouchables.” So they’ll watch Josh Brolin and Ryan Gosling as cops blasting their guns and sliding across marble floors and know it was better in Brian De Palma’s movie. That’s because De Palma didn’t carve up the space the way Ruben Fleischer has with “Gangster Squad.”