Jon Snow would likely be very cautious. He's used to dealing with magic in a more traditional Westerosi way, like with the Red Priestess. The Infinity Gauntlet would be something completely new and he'd probably be worried about its power corrupting those around him.
In this fanfic scenario, the Infinity Gauntlet could also attract the attention of the White Walkers. If they got hold of it, they could use it to spread their icy grip across all of Westeros and beyond. They might use the Space Stone to teleport their armies, or the Time Stone to reverse the defeats they've suffered, making them an even greater threat to the living.
Naruto would likely see it as a new way to protect his village and friends. He's always been about that - protecting what he loves. But he'd also be cautious because he knows that power can be dangerous. He might think about how to use it in a way that doesn't corrupt him, like how he was careful with the power of the Nine - Tails.
Daenerys Targaryen would likely see the navy destroyer as both a threat and an opportunity. She might try to either capture it and add it to her forces or form an alliance with its crew if she believes it could help her in her quest for the Iron Throne. She's used to having powerful weapons like her dragons, and this could be another tool in her arsenal.
The Lannisters would be terrified. Cersei, in particular, would see her power slipping away as Robert would surely not tolerate her and Jaime's relationship any longer. Tyrion might be more ambivalent, seeing an opportunity to perhaps gain more influence or at least not be at the mercy of his family. The Starks would be cautious. Ned's children might be resentful of Robert for leaving them in a precarious position after his death, but also might hope that he could restore some order.
The younger characters in 'Game of Thrones' like Arya Stark and Sansa Stark could be quite taken with the Beatles' music. Arya might find the rhythm and the lyrics inspiring in her own journey of self - discovery and revenge. Sansa, who has always been more into the cultural aspects of court life, would likely see it as a new form of art to be embraced. The more traditional and conservative characters like Lord Walder Frey would likely condemn it as a foreign and ungodly noise that goes against the values of the Seven Kingdoms.
Arya would likely be very defiant. She has been through so much in the original 'Game of Thrones' series that being kidnapped wouldn't break her spirit. She'd immediately start looking for weaknesses in her captors and any possible means of escape. For example, she might study their routines, when they bring her food or check on her, and plan her escape around that.
Daenerys could view the war as a fight for liberation in some ways. Just as she wants to free the slaves in her world, she might empathize with the countries fighting against tyranny in WW2. However, she would also be horrified by the death toll and the fact that civilians were so often caught in the crossfire.
Jon Snow might see it as a chance to finally make the North truly independent. He would probably use the gold to fortify the Wall and protect the realm from the threats beyond. Sansa, on the other hand, could use it to improve the living conditions of the people in the North, building more shelters and providing food during the harsh winters.
Arya Stark is very popular in 'Game of Thrones React Fanfic'. Her badass - ness and her quest for revenge make her a character that fans love to write about in different reaction - based scenarios. For example, how she would react to meeting characters from other parts of the world or how she would react if she was faced with a different type of enemy. Another popular character is Jaime Lannister. His transformation from a somewhat villainous character to a more complex and redeemable one in the original series gives fanfic writers a lot to work with in terms of his reactions to different events and relationships. And of course, Bran Stark, with his unique powers and his role in the overall story of 'Game of Thrones', is also a popular choice in fanfic.
Smaug would probably see most of the Game of Thrones characters as either insignificant or as potential thieves of his treasure. He might interact with the more powerful ones, like Daenerys, with hostility as she also has dragons. He would likely view her as a rival for dominance in the skies.