While it may en vogue to declare that your taste in movies favors “originality,” this summer only two of the 15 highest grossing films were based on an original premise.

Nevertheless, these old dogs had some new tricks in tow — Bruce Willis taught us that an action star can be older than 50; Pixar illustrated that anyone can cook (did anyone else notice that “No Reservations” and “Ratatouille” had the exact same plot, suggesting that Abigail Breslin may be interchangeable with an animated rat?); and “Transformers” proved once and for all that a movie can have a plot or robot aliens, but never both. But the five most important lessons to be gleaned from this summer’s slate of blockbusters require a little more investigation.

1. Third timers hardly charm

The three movies that sold the most tickets this summer (which were also the only three movies to gross over, fittingly enough, $300 million) have three things in common: They all were the third movie of a franchise, they all had marketing budgets approaching $100 million, and they all sucked. Together “Spider-Man 3,” “Pirates of the Carribbean: At World’s End” and “Shrek the Third” grossed $1 billion, yet it only requires a $10 ticket, two eyes and brain to discover an endless list of shortcomings in each. But third installments can also be done right: “The Bourne Ultimatum,” the best movie — blockbuster or otherwise — of the summer, proved that a three-quel can exceed the thrill of its predecessors by maintaining core elements, keeping the plot tight and introducing new and compelling motivations.

What made the first films in each series so successful was that they were something fresh and different — not just films we had already seen before, but amplified. “Live Free or Die Hard” and “Harry Potter and the Order the Phoenix” this summer, and “Casino Royale” last year, prove that by changing the format, changing directors, and changing tones, even the oldest franchises can stay fresh. We can only hope these suffering franchises follow suit in the inevitable fourth installment.

2. Down with celebrities!

A well-acknowledged rule of thumb in the entertainment industry is the bigger the stars, the bigger the box office gross, but this appears to no longer be true.

The stars of “Shrek the Third,” “Pirates of the Carribean,” “Ocean’s 13” and “Fantastic Four: Rise of the Silver Surfer” may account for 75 percent of the faces on an average teenage girl’s wall, but viewers’ time would be better spent watching a marathon of “The Singing Bee.” On the other hand, four of the five best blockbusters this summer — “Knocked Up,” “Ratatouille,” “Transformers” and “Harry Potter and the Order of the Phoenix” — have few, if any, tabloid regulars in the cast.

Much has been made of the recent surge of the exploitation of celebrities, but there may be one additional unexplored consequence — the end of the A-list star-powered blockbuster. The exposure of the biggest stars has increased two-fold over the past decade, and this familiarity undoubtedly detracts from a performance. The only top-quality movie with an A-list star was “The Bourne Ultimatum,” and, not surprisingly, Matt Damon is the summer star who has retained the greatest air of mystery.

In other words, if cocaine and alcohol didn’t do Lindsay Lohan’s career in, then “I Know Who Killed [It]”: Us Weekly.

3. Geeks save the day

Action movies with no-fear, macho leads such as the Mark Wahlberg vehicle “Shooter” are failing, and actors like The Rock (who has the emotional range of a jack-o-lantern) are being relegated to kid comedies. Meanwhile, the most successful action flicks are casting a new type of action hero in the lead.

This summer heralded the arrival of America’s new action star: the ostracized, but self-assured geek, most notably, Shia LeBeauf in “Transformers” and Justin Long in “Live Free or Die Hard.” Geek-action heroes make wisecracks about the elevated circumstances (“Dude, you just killed a helicopter with a car!”), but show bravery in the end and get the girl.

The character seems to resonate with the Internet blogger/fanboy crowd, which has become a main provider of the aggressively sought pre-movie buzz, perhaps explaining these movies’ success. The poignancy of the character also helps to explain why the suffering of old-school heroes is being increasingly emphasized in various media. Americans no longer want to believe action heroes have it easy. If Jack Bauer or Jason Bourne (or some other JB) is going to be stronger, braver and better-looking than the average fan, he better cry, too (and he does — often). The Bourne movies and “24” are heralded for being “gritty,” but that’s just a euphemism for addressing the psychological effects of harrowing situations in a “realistic” manner.

4. Marital counselors should be well-versed in science fiction

If one were to take this summer’s blockbusters as a sample, it would be easy to conclude that the most common obstacles keeping couples apart are strange science fiction anomalies.

Veritaserum did in Harry and Cho (damn you, veritaserum!), an alien parasite broke up MJ and Peter in “Spiderman 3,” while God’s orders to build an ark washed away Evan Almighty’s marriage. Most amusing was how a weird silver alien and Mr. Fantastic’s apparently extreme “love of science” was the central source of tension in his relationship with Jessica Alba in “Rise of the Silver Surfer.”

In a science fiction movie, the urge to incorporate the anomalies into the central relationships is understandable, but wouldn’t it be refreshing to include a relatable and real-world relationship tension in order to ground the otherwise unrelatable circumstances?

5. Car chase morality

This lesson is not specific to this summer and only relates to “The Bourne Ultimatum” and “Live Free or Die Hard,” but isn’t it strange how car chases psychologically present a whole new set of moral standards? If there’s one message that is delivered heavy-handedly in the Bourne movies, it is that we should not kill people unless it is totally necessary.

So why is it that staging car chases that seemingly kill dozens of innocent drivers doesn’t give the audience a second thought? John McClain drives a car the wrong way in a crowded tunnel, sending cars veering into the wall, and the audience cheers. As Bourne drives a police car into oncoming traffic, forcing cars to swerve into one another, if you add up the body count, it’s hardly different from shooting random people on the street in the leg. Of course, given the adrenaline rush only a Bourne car chase can provide, who can really complain?