When you've spent so long watching the ridiculous (but glorious) excesses of Rocky III and Rocky IV, you kind of forget how down to earth the original film is. To be sure it can't exactly be called gritty, as it's something of a grown-up fairytale, but at least it has its feet somewhere near the real world.

The film starts with Rocky fighting in some fleapit. He doesn't really seem to give a shit. He's not trying. But then near the end, his opponent, the fabulously named Spider Rico, headbutts him. This gives him the eye of the tiger and he knocks the guy out. When he's motivated, Rocky has it in him to achieve great things.

But how do you summon that will when your life is so pitiful? Rocky lives in a nasty apartment ('It stinks!'), works as a small-time heavy for a local crook, trains at a shitty gym, walks the cold, miserable streets of Philadelphia and awkwardly tries to woo the shy Adrian at the local pet store. It's not much of an existence.

One of the best scenes is when Mickey comes crawling to Rocky at the Italian Stallion's apartment asking to train him. Previously Mickey has considered Rocky nothing more than a bum and has even thrown all his stuff out of his locker. But with the World Heavyweight Champion Apollo Creed picking Rocky as his next opponent in a gimmicky New Year's bout, Mickey tries to get a piece of the action. He spends lots of time selling himself, telling Rocky about his experiences years ago as a boxer – how his face got punctured with nails one time. He even shows Rocky pictures. But all the time Rocky can't even look at him, and when Mickey is showing him his photo, he plays darts. It's quite a cruel scene, although you can understand Rocky's anger. Like he says, he needed Mick's help ten years ago.

But the scene gets even crueller. As Mickey is talking, Rocky goes to the toilet. Mickey speaks to the door and mentions that he's 76-years-old. We realise that this is his last chance at a title fight. But with Rocky still in the toilet, Mickey goes to leave the apartment. But as he's doing so, apparently thinking he's already gone, Rocky emerges from the loo. However, seeing that Mickey is still there, he turns around and walks back in. It's a real punch in the balls and we finally see how vulnerable Mickey is. And then when Mickey is walking down the stairs Rocky rants and raves about how his apartment stinks. It's actually an excellent piece of acting from Stallone and it's the one time that Rocky acts like a bastard – even when he's trying to collect money as a heavy he's still pretty damn nice. But Rocky can't be mean for long and chases after Mick to presumably say sorry and ask him to be in his corner – filmed in a long shot, there's an excellent detail when Rocky finally catches up to the trainer; before Rocky embraces him, Mickey backs away like he's frightened. Despite how loud he is, he's still only a frail old man.

Another fabulous scene is the one at the ice rink. Yes it's goofy, but that's part of Rocky's charm. He's a loveable innocent, always talking and always dispensing incoherent advice. He even says that he and Adrian make a fine couple, what with him being dumb and her being shy – as Rocky puts it, they fill gaps; they make up for each other's shortcomings. And their scenes are always sweet and well performed – you believe in them.

There's only one scene where things turn a bit queasy and that's the scene where Rocky takes Adrian back to his place. Rocky shows off his muscles by stripping down to a wifebeater vest and Adrian mentions that she's never been alone in a man's apartment before. You kind of feel scared for the poor girl, what with this horny beefcake relentlessly coming onto her. The loveable Rocky suddenly seems a bit pushy and predatory. But eventually everything works out. However, in a later scene, the tables are turned. Rocky's training for his title fight and Adrian wants some sweet loving. She keeps on pestering the guy, determined to ruin his chances of performing well in his fight. I mean, as Mickey says, 'Women weaken legs.' Therefore Rocky has to briefly push her away – she can make up for her many cockless years after the fight.

The fight itself is what you'd expect from a Rocky film: enjoyable but silly. Sure it doesn't descend into the cartoon brutality of the later films, but you still have men pounding each other mercilessly for 15 rounds (boxers were real men in the 70s – none of this 12 rounds bullshit). But even though it can't compare to the fights in Raging Bull or subsequent boxing films, the ending is hard to beat. Rocky manages to stand toe to toe with the champion and not humiliate himself, and by refusing to stay down when he gets knocked to the floor in the 14th round he finally proves his self-worth. Yeah he doesn't win the fight but he regains his self-respect, which is a major victory in itself.

And the ending with Rocky and Adrian embracing, and with the image paused at the greatest moment of Rocky's life, sweeps you off your feet and puts a massive smile on your face. Yes the Rocky films would subsequently go off into la-la land and any notion of reality would be smashed in the face, but at that moment the love of a good woman and the restoration of a man's spirit is a bigger victory than winning a boxing title. Of course Rocky didn't deserve to triumph over Taxi Driver at the Oscars, but I don't begrudge him his victory too much. Rocky is an underdog tale that wins you over with hard work and good old-fashioned working class charm.