Those big, gaudy championship belts people win for boxing, wrestling, fantasy football, and waffle eating aren't about the fashion statement… which is good because unless you're Liberace (champion waffle eater), those belts would clash with every outfit.
These belts are about the reputation. They demand respect. (Well, they label the person wearing them as a person who says, "I demand respect!") In Rocky, Rocky doesn't need the belt, because he doesn't care if others respect him. He wants to respect himself, and if he can go the distance with Apollo, he'll earn his own respect.
Every fighter has a weak spot. Apollo Creed's is his ribs. Rocky's is his reputation. A jab to his ego is the quickest way to knock him down.
Rocky is a story of growth for Adrian too. Rocky, who owns two turtles, really helps her come out of her shell. #sorrynotsorry.
It stinks to lose. And it stinks even more to lose so many times that you get branded with a permanent '90s throwback L on your forehead. For loser.
Rocky is a loser for most of the movie, but he's a lovable loser. Still, just because a loser is lovable doesn't mean he loves being a loser. Rocky wants to be a winner, and he gets to be a winner at the end by going the distance with Apollo… and losing. Even by losing, Rocky wins.
Rocky's life is so in the dumps, he's only able to get out because of a lucky break. And because he is so desperate for a change, he makes the best out of his opportunity.
Even though they are dissatisfied with their own lives, Rocky and Adrian are drawn to each other because they don't care if the other person doesn't change.
A few decades before Christina Aguilera, Rocky had ambitions to be a fighter. But ambitions are nothing without the personal drive to put in all the work and succeed.
Rocky has to find motivation to equal his ambition, and being a fighter, he's motivated by getting knocked down. A fighter always gets back up, even stronger. All those mean things Rocky's dad said to him, and Mickey said to him, stuck with him, and made him want to be better.
Rocky has lost his ambition at the beginning of the film because his self-esteem has been beaten to a pulp.
Apollo is already the champ. He's already the strongest, so his ambition is to be a celebrity, so that he will have a career after his physical strength has declined.
If boxers were simply violent people who wanted to beat the snot out of one another, they'd scrap in the streets. But the competition aspect of fighting is as critical as the visceral thrill of smacking another person in the face. Boxing is a sport, not just a brawl, and it involves training and practice before a big match in front of an audience, so everyone will know who wins and who loses.
Rocky would never get personal satisfaction from pummeling Apollo in a back alley, because it isn't hurting Apollo that's the goal. It's succeeding at the sport he loves.
Fame matters. The fight with Apollo is different from the fight with Spider Rico, not because of the difference in skill, but because of the difference in venue. Millions of people watch the championship fight, giving it much higher stakes.
Rocky is his own worst enemy, so he is competing more with himself than anyone else. He has to prove to himself that he can set a goal and achieve it.