Atheists sometimes stump for secular humanism–an idealistic version of atheism. However, a more realistic outworking of atheism is represented in neo-noir films like Serpico (1973); The Friends of Eddie Coyle (1973); Farewell, My Lovely (1975); The Killing of a Chinese Bookie (1976); L.A. Confidential (1997); Mulholland Dr (2001), &c. Some characters in these stories are rotten to the core. Others have residual common grace virtues, but they are cynical. They wish they could intervene more often to make the world a better place, but they don't stick their neck out because they know a godless world won't reward heroic virtue.
Characters in a neo-noir film believe there is no transcendent reality. This is it. Like gerbils who live and die in the confines of the aquarium. Eat, sleep, excrete, and copulate. That's all there is to look forward to.
An even more authentic depiction of godless existence is Sin City (2005). I've read reviews. I saw a few minutes of the film when it played on TV. That was the cleaned up version. Despite the brilliant cinematography, which reproduces the comic book cityscape of the original, the content was too derange for me to keep watching.