Sixth and Seventh book spoilers later on, soft spoilers throughout.
Ron is actually definitively the most intelligent of the three in terms of IQ and creativity. In the books Ron is your typical ginger geek. He loves chess, can't stand the monotony of curriculum-restricted lessons and dislike school because he is too smart for it, often acing exams etc with ease. In fact, Ron is one of the main reasons why teams-of-2 in potions class doesn't fail Hermione, who is crap at the practical element of study (he carries her and this is a major reason they end up falling in love by the seventh book, an entire snowball of bonding that's eliminated from the movies).
In the movies, they actively change events so severely so that the first movie falsely shows Ron panicking and getting cocky afterwards while they are stuck in that plant, when in the book he is actually helping the other 2 work out the incantation(s) and method to get them out of the plant. In the movies, after that, Ron plays chess and sacrifices himself but in the movies it's after the chess match that he totally annihilates without any unnecessary sacrifice (the sacrifice was necessary in order to win, no choice about it), that Hermione ends up having to choose between taking a potion that will get her back to Ron so that the move where he gets hurt (which isn't his fault) so he can avoid the pain or take another potion that will allow Harry to pass to the next stage and meet Lord Voldemort, at the price of Ron getting hospitalised from the fall from the Knight-piece. In the movies, it is almost like Ron's bad chess strategy lands them in that scenario and that he's a burden to them, whereas in the books he tells Hermione that he knew this was how it would end form early on in the match and was very willing to take the fall.
As the books evolve, you get to see that this Einstein-esque 'scruffy looking but very clever' genius was put in Gryffindor, rather than Ravenclaw, more out of the same choice made under the hat's pressure that Harry made in order to get put there rather than in Slytherin. In other words, Ron chose to be put in Gryffindor rather than Ravenclaw in the same way that Ginny, who clearly belongs in Hufflepuff, chose to be put in Gryffindor. Ron isn't brave, he isn't dumb and is so far from the goofy oaf that's portrayed on screen that it actually shocked me how badly they could fuck up the portrayal of such a major character in the series.
Ron was actually the cool-headed one of the three, in the books. In the movies he's the most volatile and emotionally driven. The only time that Ron makes an emotional decision in the books is when he leaves Hermione and Harry in the seventh book. Mostly, he's a smooth talking, level-headed suave geek. He also is the most cunning of the three, which is also not portrayed in the movies, they actually give him a sense of naivety and cuteness that is extremely anti-Ron from the books. Ron is very close to the Malfoys in his general demeanour in the books, that sort of cold, almost snobbish charisma. Like he is a general 'prick' but pulls it off well and draws people in with the confidence, the closer they get to him.
If you are curious of the reason that Ron is definitely supposed to be this way, as opposed to the way he's portrayed in the movies. it's because he was the 'serious one' out of the sibilings he grew up with. Percy was the 'serious one' but was leaving the household as Ron began to mature. His father didn't mind the 'silliness' of the others but his mother really liked him a lot, because he was a down to Earth guy she felt understood the core Weasley values (think left-wing values, that's basically what their family stands for even thought it's an elitist bloodline). While being left-wing in general, Ron was most certainly Libertarian (much like myself he saw no reason to give one up for the other) and believed authority to be almost innately corrupt, especially when it tries to tell you one way to do things (whether make a potion or solve a mystery) is correct when other ways are available.
It was Ron, in the books, who helps them realise who the philosopher's stone belongs to and why. Hermione identifies the 'who' as in linking it to the guy but Ron helps them realise it's an immortality gem by being very strongly involved in the conversation. In the movies Dumbledore tells Harry on the bed, whereas in the books Harry had already worked it out with Ron and Hermione and Dumbledore simply nods his head in essence.