By now, you've no doubt heard the news: 'The Expendables' is the number one movie in America for the second week in a row. That's right: A movie starring Sylvester Stallone as a good guy has had back-to-back blockbuster weeks for the first time since ... well, so long ago that Wesley Snipes was still relevant.

While many prognosticators predicted the movie would win its opening weekend, not even Sly himself could have seen this kind of success coming. And at $64 million and counting, it continues to rake in money despite less-than-stellar reviews.

But on second glance, maybe the throwback action flick's whopping box-office haul isn't that surprising, after all. Why? Let's break it down.

By now, you've no doubt heard the news: 'The Expendables' is the number one movie in America for the second week in a row. That's right: A movie starring Sylvester Stallone as a good guy has had back-to-back blockbuster weeks for the first time since ... well, so long ago that Wesley Snipes was still relevant.

While many prognosticators predicted the movie would win its opening weekend, not even Sly himself could have seen this kind of success coming. And at $64 million and counting, it continues to rake in money despite less-than-stellar reviews.

But on second glance, maybe the throwback action flick's whopping box-office haul isn't that surprising, after all. Why? Let's break it down.

1. Weak competition
The movies that opened on Aug. 13 were a microcosm of the current trends in movies today -- men vs. women vs. nerds. On the female-friendly side, there was 'Eat Pray Love' -- which had an audience consisting of fans of the sappy Elizabeth Gilbert book and of Julia Roberts. There was the whimsical film 'Scott Pilgrim vs. the World' -- whose niche audience consisted of graphic novel and Michael Cera fetishists. And then there was a broad action movie starring Sylvester Stallone.

There was a lot to choose from this past weekend, but nothing that was expected to make much of an impact. When your main competition is 'Vampires Suck,' you're probably going to do okay.

The Expendables2. Predictable entertainment
Quick: Describe the plot to 'Scott Pilgrim vs. the World.' Or 'The Switch.' Their plots are simply too confusing to market effectively. But there is only way to describe 'The Expendables' -- a bunch of old dudes blow stuff up.

Sure, you can read what the nerds on Twitter are saying about 'Scott Pilgrim' -- about how it was the greatest movie ever! But this is also the same demographic that predicted good things for 'Jonah Hex' last year.

Say what you will about Stallone's formula, but regular people (you know, the ones who don't obsess about movies and who actually drive the box office) knew exactly what they were going to get before the movie even started.

3. No "Wait for DVD" factor
Some movies you just have to see on the big screen. Most of these are effects-laden spectacles heavy on gaudy action scenes. We believe that last sentence is the exact description used by Lionsgate to market 'The Expendables.'

4. Action stars aplenty
Stallone's latest Rocky and Rambo installments did marginally well, but those had pre-existing audiences. If a commercial had started running in advance of 'The Expendables' advertising, "Sylvester Stallone is ... Barney Ross!" and the name of the film had been just "Ross," would you -- or anyone -- have seen it?

But here, it's not all on Stallone. Not only would any lingering Sly fans want to see this movie in the theater, but aficionados of Jet Li, Jason Statham, and Dolph Lundgren would, as well. (Okay, there are no fans of Dolph Lundgren.) Bonus: the ability to see Arnold Schwarzenegger, Bruce Willis and Sylvester Stallone -- the holy triumvirate of 1980s action stars -- on the screen at the same time proved too much for male Generation Xers to pass up.

The lesson seems to be: If you're going to make a summer action movie, make sure to assemble the right cast, don't take too many risks and just give the people what they expect. That may be kind of depressing, but it appears to be true.

For any compliments or complaints, you can contact Mike Ryan on Twitter.