“Entourage” (Claudette Barius/ Warner Bros. Entertainment) and “Sex and the City” (Warner Bros.)

Two HBO comedies, each about a group of four core friends trying to succeed in life and love. One centers on men in Los Angeles, the other features women in New York. They both have huge fanbases and nearly 100 episodes, racking up similar accolades and awards along the way.

Yet when it came to movie versions (both even released in the same time frame at the beginning of summer movie season), the two series took very different paths: The “Entourage” movie, which opened on Wednesday, is largely considered a flop: It took in a little more than $18 million over five days, opening at No. 4 at the box office. Meanwhile, back in May 2008, “Sex and the City” made an impressive $57 million haul in its opening weekend, easily becoming No. 1. The movie went on to become a giant success, raking in $415 million worldwide, and spawned a much-derided sequel that made $228 million overall.

[Everyone hates ‘Entourage’ now. When did the world turn on the hit show?]

Why did seemingly parallel journeys diverge at the critical moment of making a film adaptation? It’s highly unlikely that reviews were a factor: Although most critics hated “Entourage” adaptation, they weren’t exactly thrilled by the “Sex and the City” one either. So we offer three potential reasons for the lopsided results:

1) “Sex and the City” always had more viewers.

This is probably the most obvious: While “Entourage” debuted to about 2 million people, “Sex and the City” was already averaging around 6 million viewers a week. That pattern held true throughout the whole series: Approximately 10 million fans tuned in to catch Carrie Bradshaw say goodbye in February 2004. But when Vincent Chase and the gang bid farewell in September 2011, only 3 million people watched (and that included a later repeat the same night).

[Movie review: Jeremy Piven enlivens ‘Entourage,’ which plays out like a long TV episode]

2) “Sex and the City” quit while it was ahead. 

When “Sex and the City” ended, fans still craved to know more about the characters, as the finale wrapped up long-running story lines that built steadily over the years. Even though there were conclusions, there were also cliffhangers: Carrie finally ended up with Mr. Big, Charlotte got a baby, etc. Given that they had an investment in these story lines, viewers were understandably curious about what happened next.

As for “Entourage,” the show was sliding for awhile, and interest in the show waned. In the series finale, Vince was on his way to marry a woman he barely knew. While some fans may have been mildly curious about power-agent Ari Gold quitting Hollywood to run off to Italy with his wife, there wasn’t an urgent need for the stories to continue.

3) “Sex and the City” was a movie aimed at women.

Whenever a movie marketed at an underserved audience does well, the industry generally dubs it a “surprise” hit. But really, was it any shock that a female-targeted movie did so well when there are so few other options to choose from? “Entourage,” on the other hand, faced plenty of male-demo competition, from “Mad Max: Fury Road” to “San Andreas.” And because it was a movie that already appealed specifically to fans of the show, it simply got lost in the shuffle.

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