Oh friend, you may not know it but you just shouted out RELEASE THE KRACKEN and now I will proceed to come at you with my words.
Ron and Harry’s friendship is one of the most important relationships in this entire series. A lot of focus is put on Harry’s relationships with father figures (Sirius, Dumbledore, Lupin, his real father - it’s a coincidence that they all have to die for Harry to realize he must stand alone), but Ron is such an integral part of Harry and who he is and where he belongs that it’s second nature for Harry to rely on Ron, and it’s only when Ron is taken out of the equation (GOF and DH) that it starts to dawn on him how highly he values Ron, and how much he loves him.
Look at these two kids, look at their lives; you’ve got Harry, this lost and lonely kid, who has never had a friend, or someone to confide in, or someone whose kind of stuck in the back trying to muddle their way through everything. He’s been met with hostility or coldness his whole life; and yet, he retains a strange optimism, like he knows his life is going to get better, because it can’t be any worse than what is was before.
And then you’ve got Ron. Until he gets to hogwarts he’s lived his life as the youngest Weasley brother. He’s perpetually in someone’s shadow, and he just wants to become his own person, and that’s what Hogwarts is for him - a place where he’ll become Ron, and not just another Weasley. In this, he’s just like Harry - Hogwarts is a fresh start for both of them.
And then, by miracle or by design, they find each other. These two eleven year olds thrown into uncharted waters, on what is unmistakably an adventure, and they - wonderfully, amazingly - become best friends. It’s Remus joining the Marauders and finding people who understand him - it’s Severus approaching Lily and telling her about magic. Friendship is such an important theme in these books and I would argue strongly in favour of Harry and Ron’s being the best friendship within the series.
Harry and Ron represent, to one another, something the other lacks. To Harry, Ron is the family he has always wanted. He goes to the Burrow and sort of sits around in wonder, not only at this magical home but the people in it - the wild and dysfunctional family, and their errant pets and the gnomes in their garden and their beautiful family dynamic and all the things Harry’s wanted, but never been able to have and it’s just… stunning to him. And it’s something Harry would never, ever give up.
And then Ron… Ron more of a typical teenage boy. To Ron, Harry is rich, and famous, and has never felt like he was not good enough, and these are the things that Ron desires. It’s all there, in the book - Harry goes to the Mirror of Erised and sees himself with a big family (like Ron’s) and Ron sees himself as Quidditch captain and Head Boy (aka popular and (relatively) famous, like Harry). Ron and Harry are each other’s foils. And it’s part of what makes them so cohesive - they don’t always get on, but they’re almost dependent one another, because it’s really like they’re brothers. It’s like they’ve known each other for their whole lives.
This, of course, is extrapolated by the crazy shit they get themselves into. It’s one of those unspoken things, but Ron sticks by Harry through a lot. Giant chess sets and underground caverns beneath girl’s toilets and polyjuice potion and getting beaten up by Harry’s father’s friends - not only does Ron stick by Harry, he throws himself right in there next to him. His anger in DH isn’t sudden, it’s overdue, and I think it says a lot about the nature of the Harry/Ron relationship that it takes a Horcrux to tear them apart.
At the end of the day, Ron is the one who is sitting next to Harry when his scar starts to hurt; who literally breaks the chains that hold him down at Privet Drive; who takes Harry into the magical world; who becomes his family. These two have always been on the slow road next to each other, and it’s a friendship so strong not even fucking Voldemort can break it. And that - that’s some powerful mojo.
As for the movies and how they completely destroyed this relationship, this tag I wrote a while ago basically sums up my feelings on that:
“Harry Potter has to go into the lake and find his Wheezy —-”
“Find my what?”
“—- and take his Wheezy back from the merpeople!”
“What’s a Wheezy?”
“Your Wheezy, sir, your Wheezy - Wheezy who is giving Dobby his sweater!”
“What?” Harry gasped. “They’ve got… they’ve got Ron?”
“The thing Harry Potter will miss most, sir!”