Ron's family—The Weasleys—is made of up everything that Harry never had growing up: love, caring, and magic.
When Harry first walks in the door of their house, the Burrow, he sees household items moving on their own and spells working all around. The Weasley home may be humble but, to Harry, it's perfect.
Sure, the next thing that happens is Mrs. Weasley chews them out for flying home in the Ford Anglia, but Harry knows that at least she cares about her sons. That's more than he can say for Uncle Vernon or Aunt Petunia. They'd probably be glad if they got a letter saying he crashed in a flying car and got burnt to a crisp.
The Weasleys also don't worry about money or appearances. Unlike some wizarding families we know. While the Malfoys are always trying to show off their money or their power, the Weasleys are just concerned with doing what's right and being kind. Maybe that's why Harry likes them all instantly.
Mr. Weasley works for the Ministry of Magic and in the Misuse of Muggle Artifacts Office and he's totally obsessed with Muggles and their culture. Bigots, like Lucius Malfoy, see this as a reason to attack the Weasley family:
LUCIUS MALFOY: Busy time at the Ministry, Arthur, all those extra raids? I do hope they're paying you overtime. Though judging by the state of this, I'd say not. What's the use in being a disgrace to the name of wizard if they don't even pay you well for it?
MR. WEASLEY: We have a very different idea about what disgraces the name of wizard, Malfoy.
LUCIUS MALFOY: Clearly. Associating with Muggles. And I thought your family could sink no lower.
See, the Weasleys are pure-blood, but they don't buy into all this nonsense about certain types of wizards being superior to others. Since they're not talking up their pure-blood privilege left and right lots of people don't like that. But the Weasleys don't mind the haters. They're just concerned with doing what's right.
Now if someone could just explain to Mr. Weasley what a rubber duck is for, we'd be all set.