Sakura might be the most surprised. She has always been very close to Naruto, and seeing him as a powerful future version would be quite a shock. She might be amazed at how he has developed his skills and also how he has changed as a person.
I think Sasuke could also be extremely surprised. Given his complex relationship with Naruto, seeing a future Naruto would make him re - evaluate their past and future interactions. He would be taken aback by Naruto's growth, especially if Naruto has achieved things that Sasuke hadn't even considered possible.
Honestly, it's hard to say. Dumbledore would be amazed at Harry's future self, but Harry would also be taken aback by seeing Dumbledore in a different time. It could depend on the circumstances of their meeting. If Harry comes back to a time when he thought Dumbledore was dead, then he would be extremely shocked. On the other hand, if Dumbledore has been expecting some sort of time - traveling encounter, he might be less surprised than Harry.
Hulk could be the most surprised. He doesn't always pay attention to the subtleties of character growth. But seeing Peter, who was once a small and somewhat inexperienced hero, now be this confident and powerful figure from the future would really catch him off - guard. He might even be a bit intimidated at first by the new - found strength and presence of future Peter.
Probably Naruto. Since Minato is his father, he has always longed to know more about him. Meeting Minato and his team would be a dream come true for Naruto. He would be eager to hear stories from his father's past, about his training, and how he became such a great ninja. Naruto might also want to show off his own skills to his father and the rest of Team Minato.
Sasuke would also be a likely candidate. His journey is filled with so many twists and turns. His future self could show him an alternate path or confirm that the path he is on is the right one. Maybe he becomes more at peace with his past and his clan.
The relationship between Naruto and Sasuke could become more complex. If Sasuke's future self has accomplished great things but at a cost, Naruto might question his own ideas of success. For Sakura, seeing her future self might make her more assertive in her relationship with the boys, especially if she has become a very respected ninja.
Well, one possibility is that future Naruto has some sort of warning about a great danger that is coming to their present time. So, he travels back to meet Team 7 to prepare them. Team 7 would then have to deal with the knowledge that they are somehow crucial in preventing this future threat. And of course, there would be a lot of emotional moments as they see what Naruto has become.
I think Kakashi's interaction with Minato would be very interesting. Kakashi was Minato's student. Meeting his sensei again, especially with Team 7 in tow, would bring back a lot of memories. Kakashi could show Minato how he has grown and passed on Minato's teachings. And Minato could give Kakashi some new insights based on his own experiences.
It could be the newer protagonists who are more surprised. For instance, if a protagonist from a more recent game meets Ash, who is like a legend in the Pokemon world. They would be in awe of his adventures and his reputation, while Ash might be more used to strange encounters compared to them.
Naruto would probably be the most interested. He loves making new friends and Gohan's power would surely catch his attention. He'd be eager to learn about Gohan's world and his abilities.
I think Naruto would interact a great deal with Hinata. Hinata has had a crush on Naruto for a long time. In Team 8, she might be more open with her feelings. Naruto, being kind - hearted, would notice her kindness towards him. They could have some sweet moments together while also training and going on missions as part of the team.