Harry Potter is the kind of movie (or movie franchise) that can sort of be considered a Christmas movie... but largely because people want to watch it and its special brand of snowy magic at Christmas, rather than because the holiday is central to the plot. There are some amazing Christmas scenes in the franchise, of course - snowy days at Hogwarts, the Yule Ball, even just Christmas at the Burrow, but the series doesn't delve too deeply into how wizarding traditions different from the Muggle holiday.
It seems that witches and wizards still gather round for family time, good food, pulling crackers, and giving gifts - but no mention is made of the Christmas movie. Wizards don't seem to have films or TV in quite the same way (although this may just not be mentioned), but if they did, we know exactly which muggle movie would be perfect for each of the Weasleys.
Bill - The Nightmare Before Christmas
Bill, a curse-breaker at Gringotts and always someone who was a bit of a rebel, isn't going to go for the usual Christmas fare. After he was wounded (and became a little bit wolfy) during the war, he would be even less likely to settle in for some cheesy movie. However, he would probably get a kick out of The Nightmare Before Christmas, with its gothic flair and blend of Christmas and Halloween. Fleur might be less impressed, though... she doesn't seem like quite the type to go for Jack Skellington.
Charlie - Die Hard
Charlie doesn't get much screentime in the movies, but he's more developed in the books, as someone who works with dragons. He's definitely active, physical, and not the type to take on a desk job - which is why he'd probably love Die Hard. Sure, there are those who would argue it doesn't count as a Christmas movie, but Charlie is not the kind of guy to really care what anyone else thinks. He'd love the action and appreciate John McClane's actions - he may even be brave enough to take on a dragon, should one ever appear in his fictional world.
Percy - Love Actually
Percy might be the least-loved of the Weasleys, but he's not bad at heart. It's just that he is the kind of guy who wants order in the world, and he wants to follow the rules and fit in with how things are supposed to be. This is why he gets caught up with the Ministry and strays from the family, but his good heart is why he returns to them in the end.
Love Actually would be the perfect choice for him, as this is a film that has real heart, is a total classic, and shows how everyone is connected - a classic that someone like Percy would definitely appreciate.
Ginny - Klaus
Ginny isn't the kind to go for a super-schmaltzy holiday romance, but she's also not the type to completely dismiss some earnest Christmas cheer. Klaus would be the perfect choice for the only Weasley daughter, as it's a film that is a little bit different, that has a unique story, and that isn't purely Christmassy. It's just like Ginny - incredibly hard to put in a box, and absolutely wonderful.
Arthur - Elf
Arthur has a lifelong fascination with muggles, even though he seems to struggle to actually understand how their world works. As a result, he would fall in love with Elf, and probably relate to Buddy a little too much! Both Buddy and Arthur can find themselves in worlds that are unfamiliar - but not completely unknown to them - and their positivity and natural curiosity carries them through. The only potential issues with Arther watching Elf is that he may not understand why Buddy is so funny... he's just naturally interested, the same way Arthur would be!
Molly - It's A Wonderful Life
Molly is a bit of a traditionalist, and she loves Christmas traditions. The matriarch of the Weasley family, Molly would want something that is warm and fuzzy, and that would be a good fit for the whole family. She would also love how positive and family-oriented It's A Wonderful Life is, making this a perfect holiday choice for her. She may even start requiring the family to watch it every year, much to the annoyance of her (very loving) family.
Fred & George - Home Alone
Could there be a better choice for the pranksters of the Weasley family? Fred and George are known for their jokes, even opening up a joke shop after they leave school (although, of course, both brothers don't survive to the end).
These practical jokers would admire Kevin and his ingenuity - and may well end up taking a little inspiration from the inventive youth. Of course, they would find ways to improve upon everything with magic, but this would still be the perfect film for them.
Ron - The Christmas Prince
This may come as a bit of a surprise, and Ron would probably never admit to it, but at the end of the day he would probably love this kind of popular cheese. For one thing, Ron has always wanted to be popular, and a film like The Christmas Prince would pique his curiosity - seeing the kind of response that it gets, Ron would not be able to prevent himself watching. And he's got a bit of a sensitive and romantic streak - as fans know from his relationships with both Lavender and Hermione. After spending his teen years fighting Voldemort, he'd probably love something as simple and charming as this.