It’s July 1, 2012, and the latest incarnations of Spider-Man and Batman arrive on our screens this month. That’s appropriate. These guys have a lot in common.

We tend to think not. We tend to think of them as opposites. Batman is DC, Spider-Man Marvel. Batman is silent and dark, Spider-Man gabby and colorful. Bruce Wayne is rich, Peter Parker poor. Spidey has the proportional strength of a spider, Batman is just a strong dude, dude.

Moreover, neither can sustain the other's mood. When a Batman movie goes for lighter and gabbier, you wind up with crap like George Clooney in “Batman & Robin” (1998). When a Spider-Man movie turns dark and vengeful, you wind up with crap like the evil Spider-Man in “Spider-Man 3.”

They’re oil and water, these two. They don’t mix.

Our biggest box-office superheroes
But at the box office they’re our two most popular superheroes. They keep trading off bragging rights. Tim Burton’s “Batman” set the opening-weekend box-office record with $40 million in June 1989 and was the No. 1 movie that year. Sam Raimi’s “Spider-Man’ set the opening-weekend box-office record with $114 million in May 2002 and was the No. 1 movie that year. “Spider-Man 3” may have set a new opening record with $151 million in May 2007 (and was the No. 1 movie that year), but Christopher Nolan’s “The Dark Knight” took it back again with a $158 million opening in July 2008 (and was the No. 1 movie that year).

Here. These are the top five superhero-movies of all time:

• The Avengers (2012): $606,298,000
• The Dark Knight (2008): 533,345,358
• Spider-Man (2002): $403,706,375
• Spider-Man 2 (2004): $373,585,825
• Spider-Man 3 (2007): $336,530,303

Adjust for inflation and you get more Batman:

• The Avengers (2012): $606,298,000
• The Dark Knight (2008): $588,314,100
• Spider-Man (2002): $550,319,200
• Batman (1989): $498,600,600
• Spider-Man 2 (2004): $476,457,300
• Superman (1978): $454,276,400
• Spider-Man 3 (2002): $387,401,200
• Iron Man (2008): $351,218,400
• Batman Forever (1995): $335,063,500

So why are these guys so popular?

The dictionary definition of a superhero
Watch Sam Raimi’s “Spider-Man” again and notice how much he borrows from Tim Burton’s “Batman.” Both movies are scored by Danny Elfman. Both heroes battle grinning maniacs. Both movies give us city-wide celebrations, complete with parade balloons, in which, backed by the R&B singer of the day (Prince, Macy Gray), the supervillian attacks the populace. Both Burton and Raimi come out of the horror genre (“Evil Dead”; “Beetlejuice”), and both include scenes in which the hero is seen as the horror by petty crooks: the opening rooftop scene of “Batman”; the warehouse/carjacker in “Spider-Man.”

“What are you?” the petty crook asks in the beginning of Tim Burton’s “Batman.” “I’m Batman,” Batman replies.

“Who am I?” Peter Parker asks us at the end of Sam Raimi’s “Spider-Man.” “I’m Spider-Man.”

Beyond the movies themselves, both superheroes tend to fit what we think of as the dictionary defintion of a superhero: They 1) have secret identities, 2) prowl the night in search of crime, because 3) they’re attempting to cleanse themselves of a past tragedy.

We think of this as the dictionary definition but it really isn’t that common. Most of the superheroes of Batman’s “Golden Age” generation didn’t have a psychological motivation to fight crime; they did it because it was right (Superman), or because they’d been detectives (The Spirit), or because Hitler’s hordes were on the march (Captain America). Most of the superhero identities of Spider-Man’s “Silver Age” generation, meanwhile, were either known (The Fantastic Four, X-Men) or irrelevant (Hulk), and they rarely bothered with petty crime. They were too busy saving the world from Galactus.

But Spider-Man and Batman bothered. Because both are bothered.

Revenge vs. guilt
As a child, Bruce Wayne sees his parents murdered by a petty crook and burns with a desire to get the bastards. That’s why he’s Batman: he wants revenge.

Batman: It's their fault.

As a teenager, Peter Parker’s Uncle Ben is murdered and he burns with a desire to get the bastard; then he realizes he had the chance to stop the dude before the murder and didn’t. That’s why he’s Spider-Man: he’s overwhelmed by guilt.

Spider-Man: It's my fault.

But is such psychological motivation a key element to box-office success?

Let’s look at “Iron Man,” the No. 8 movie on the list above. Does Iron Man fit the dictionary definition of a superhero?

Pretty much. He may not fight street crime but he does fight war crimes, and he's psychologically motivated to do it. For the first part of the movie, he’s held hostage by terrorists, who kill his friend and savior, Yinsen, so he wants revenge on the bastards. At the same time, he’s been creating and supplying and getting rich off of weapons for years, so he’s guilty, too, and needs to cleanse himself. He's combines the motivations of both Batman and Spider-Man. Nice trick. Of course, at the end, he gives up his secret identity (in a totally cool move), and besides the box-office success of “Iron Man” certainly had more to do with the movie's kick-ass special effects and Robert Downey Jr.’s kick-ass wit and charm. But superhero motivation doesn’t hurt. At the least, it helps the movie make sense.

Let’s go the other route. Are there examples where the superhero fits the dictionary definition and his movie still bombs at the box office?

I can think of one: “Daredevil” (2003), starring Ben Affleck. Matt Murdock’s father is killed by mobsters, which gives Matt the motivation to fight crime, and in the end he confronts his father’s killer. “Daredevil” didn’t bomb, so to speak; it raked in $102 million. But it bombed by Batman and Spider-Man standards. It was the 27th biggest movie of the year, not the 10th or fifth or first. Psychological motivation for your superhero may help, in other words, but you still have to put something decent on the screen.

Superman: What’s my motivation?
How much does motivation help? Of the nine most popular superhero movies listed above, Batman has a motivation, Spider-Man, too, and Iron Man two. As for the Avengers? They’re psychologically unsuited to team up but supremely motivated to save the world. That's the Stan Lee/Jack Kirby twist. We fight in times of peace but unite in times of war. You could say it's the story of America. Or it's the story America likes to tell about itself.

I hope saving the world is part of Superman’s motivation in next year’s “Man of Steel." Superman was the first true superhero, and, back in 1938, he fought crime and injustice just cuz. But ultimately Superman’s origin isn’t much different from Batman’s. Both lost their parents. Batman lost his to crime, and that’s why he fights crime. Superman? He lost his parents, and his entire planet, because nobody could be bothered to listen to the apocalyptic warnings of its scientists. So shouldn't he fight ... that?

I know. A downer. Tough to dramatize. Preachy. At the same time, it might resonate a little. It might even give the popcorn-munching crowd a little psychological motivation of its own.

Superman: Is it your fault?