I have a friend from college that I like to drink with, a lot. We're neighbors now, so we get to do that all the time. Our favorite activity is to get absolutely shitfaced and watch BACK TO THE FUTURE, while discussing the massive, glaring issues with the movie, like the entire plot and all of the characters. That being said, it is one of my favorite movies.
McFly's priorities are so fucked up that the only thing he does with the Space-Time Continuum is screw with it to make his parents less nerdy and his teenage self more spoiled. You know what else happened between 1955 and 1985? Significant tragedies that, if prevented, likely would have made the world a better place. I’m a pretty selfish person, and I’m pretty sure I would have given at least 13 years of my life (even as a teenager) in order to save someone as important as Martin Luther King, Jr. High school sucked anyway.
Also, he doesn't remember any of his supposed childhood now that he's changed everything, so he's clearly going to be institutionalized. Going back in time to name himself after himself turned Marty into a different person by turning himself into the person he was when he went back in time. Time travel movies hurt my brain.
There are some serious fucked up implications about him changing his entire family by fucking with the past. Obviously, it stands to reason that he would have changed as well. At the very least, his memories of his parents and older siblings would be different, because they are completely different people when he returns to 1985. Hell, he’s lucky they still live in the same fucking house when they’re the more successful versions of themselves!
And his girlfriend (the one who plays a completely unnecessary role, adding nothing to the story) should notice immediately that he experienced some serious trauma during that event in the mall parking lot when fucking Libyan terrorists attack him and his weird old professor friend (also some weird implications there, with a high schooler hanging out with a much older man). Seriously, at the very least, she should think he was suffering from serious PTSD when he returns to 1985 and is inexplicably surprised by the family he grew up with.
In spite of all the massive problems caused by time travel, Marty’s mom still tries to bang him when they’re both teenagers, which is extra fucking creepy. In fact, that whole love triangle-ish thing is the reason studio after studio passed on the script. I’m happy that Universal eventually sucked it up and took the plunge, because I refuse to live in a world in which BACK TO THE FUTURE doesn’t exist. I would build my own flux capacitor and travel back in time and make the movie myself.