Like the movie Planet 51, but with a character that obeys the laws of common sense of what a person would actually do in those situations. (and no aliens other than us 50's people thinking that future would be the alien.) Because seriously anyone from today would go back there and say the future sucks and it's not what you think it would be, it's hell. Plus if I did, I would've brought the proper equipment to show what the future would be without any complications, which would mean showing some of the technology that we would have in the future, on civilian level and some of the military, not to mention some of the advances in fields like Medicine and others. However, then I would also talk about the issues of the modern day, from politicians to racial issues to social, etc. The biggest issue that I would tell them about is the endless warfare that is constantly happening and probably will continue to happen for centuries to come. This also includes showing, for example, trailers for This War Of Mine, mainly of the one that's side-scrolling, as a way to show the reality of war that the movies and veterans don't tell you about from a realistic perspective if you were actually there.
Also, I'd probably make a show where I talk about monster movies and stuff from an artistic viewpoint, instead of saying that they're terrible, which I will admit some of them are and I would say that, but not in the way of saying that they're using outdated techniques for movie making. That's stupid. I also think that I'd talk about sci-fi alien movies from a realistic view, mainly on the topic of this:
Ok let's be serious about this, do you really think that aliens would care about us and if they really did invade, they would've bombed us from orbit with no resistance. And besides, they would know way more about us then we do ourselves, they'd know our full history while we have problems of people altering it for stupid reasons, and the fact that there are no alien encounters because it's impossible to know since there are so many fakers out there who claim it but have no proof and if there is proof it's impossible to be sure it really is proof. Plus the only way to really know is if there was a fleet that entered the airspace of a major city, like New York and requested an audience for diplomatic meetings between both species, and having similar ships show up EVERYWHERE around the world to show everyone that this isn't fake!
Ahem, anyway this is something that I think would be interesting if someone decided to make a movie of this idea. Since it's something that does come up in my head when I see representations of the past in video games and movies.
(PS, and I'd tell everyone to LAY OFF THE SCI-FI COMICS!! DON'T LET THEM GET TO YOUR HEAD TOO MUCH!)