Batman: Arkham City may have only been on sale for a week (in the US, 4 days over here), but it has already topped a staggering 4.6 million unit sales worldwide. And that's without the PC version included, which is yet to be released - on 8 November in the UK.

And having played it ourselves, it's easy to see why. Indeed, it's rare for reviews around the 'net to give it less than 9 out of 10.

But what makes it different to many other action games out there? Why has it captured the imagination of the public in such spectacular fashion? The answer is simple, according to developer Rocksteady Studios, and its narrative designer Paul Crocker: Batman.

"Batman is an awesome character who works on so many levels and for so many people," he told Pocket-lint in an exclusive one-to-one briefing. "He's a lunchbox for kids, and he's the guy in the Frank Miller book [The Dark Knight Returns] for people my age.

"He is somebody they grew up with, getting comics when they were tiny tiny kids, being shipped over in post-war containers. And for people who went to graphic novel stores or comic stores. Or have seen the movies.

"It's not just one thing, and that's what's so great about the character," he explained. "And we get to do our version of him."

But could the same be done with another comic book character? Would another icon be so successful in game form?

"Honestly," said Crocker. "To make a game, I have many comic book dreams. But none of them are as good as Batman.

"I love loads of stuff from all the different publishers. I love Hellboy. We're not doing a Hellboy game, that's absolutely not happening, but that's a personal fave.

"We love Batman, though. Who can complain about working on a Batman game?"

What's the betting on a final part of a Batman: Arkham trilogy then? Hmmm...

What do you think? Would you like to see a third chapter for Batman? Let us know in the comments below...