The reasons for this lie in the basics. For starters there's an original concept and storyline (of sorts). At a time when Hollywood's summer offerings have plunged to new depths of laziness, spinning out another trove of Spiderman movies less than a decade after the Toby MaGuire reboot, Guardians' unfamiliarity feels like a breath of fresh air.
Or to put it another way, it isn't a sequel and doesn't involve Michael Bay.
Bay's absence also allows for two other things, subtlety and humour. Guardians is refreshingly self-deprecating - one sequence sees our part-time hero, full-time lothario, Quill (Chris Pratt), defeat an evil overlord by confusing him with a dance off. Moments of lunacy such as this leave the audience guessing.
At points it ends up satirising the genre. For instance, Quill begins life on Earth, permanently attached to his Walkman. Even in the galaxies, 80's music remains very important to him as a reminder of his childhood. This leads to plenty of jokes about Footloose and Kevin Bacon, trusting in the audience to understand and going a long way to ensuring the film's broad appeal. Parents laugh, and kids look as confused as the alien creatures Pratt is spilling these jokes to, yet still giggle at watching a space ranger dance around to Rupert Holmes’ Pina Colada hit record.
Underpinning all this madness are some memorable characters packed with personality. The star is undeniably Groot, a benevolent and very lovable tree creature voiced by Vin Diesel. The only words he knows are "I am Groot" which suits Diesel's dialogue skills perfectly. Somehow he turns out to be the best novelty character since Ja Ja Binx. To top it off, he's best pals with Rocket (Bradley Cooper), a tempestuous Racoon very similar to StarFox. The pair meet Drax the Destroyer (David Bautista), the spitting image of Kratos (the development team clearly love computer games) and Gamoa (Zoe Saldana). Together they team up with Quill to defend the galaxy.
It shouldn't work on paper, but sometimes letting go and having some fun yields the best results. Guardians is a hit because it leaves audiences entertained. Blockbusters used to do that.
The new Star Wars its work cut out. I AM GROOT.