The original Star Wars films had a lot of plot changes and deleted scenes. If these parts from the original scripts weren't cut out, the new movies would've been a completely different story from what they are.
The first changes are in a New Hope. Originally, Star Wars was the subtitle. The film was called Journal of the Whills (I can imagine "battle" or "journey," but not "journal"), and the subtitle was Star Wars.
The next major change was that Luke Skywalker was going to be a girl. Luke was going to be a sixteen year old girl who fell in love with Han Solo. For some reason, the sketches of her looked very similar to Rey in the new movies.
At the end of the movie, Darth Vader kills Obi-Wan Kenobi with his lightsaber. But, originally, Obi-Wan was going to survive. He was supposed to survive all the way to the next movie in the saga, the Empire Strikes Back.
Another big change in a New Hope is that Luke's last name was going to be Starkiller instead of Skywalker But it was a little too violent, and it sounded more like a Sith than a Jedi, so George Lucas changed it to Skywalker. Later, Starkiller was reused as Darth Vader's apprentice.
Now we're moving on to the Empire Strikes Back. A really big change was that Darth Vader wasn't going to be Luke Skywalker's father. Originally, Luke's father was going to be in the movie, but he wasn't Darth Vader.
The next big change was that Luke's sister was going to be revealed in the Empire Strikes Back instead of Return of the Jedi, and it wasn't going to be Leia. His sister was going to be another girl named Nellith.
This one is a little weird. It was going to be revealed in the movie that Darth Vader lived in a giant castle with his pet gargoyles. The Empire Strikes Back would've been very different if they had went with this.
Also, Lando Calrissian was going to be a clone of a soldier from the Clone Wars. If this had been kept in the movie, you would've known more about the Clone Wars before the prequels came out.
The next and final movie in the original trilogy is Return of the Jedi. Originally, the movie was titled Revenge of the Jedi, but then George Lucas decided that Jedi should never take revenge, so he changed it to Return of the Jedi instead.
At the end of the film, Darth Vader saves his son and kills the Emperor. Because of the Force Lightning, he dies, too. Originally, Darth Vader still was going to die in the same way, but right after he takes Vader's mask off, Luke was going to hold it up to his own face, showing that he would become the next Vader. But Luke never showed any anger, and he doesn't seem like the kind of person who would be a Sith, so George Lucas cut that out of the movie.
Originally, Han Solo was going to die, which would change everything in the Force Awakens. The whole story would've been different because Han would've already died, and Kylo Ren would never had existed. And without Kylo Ren, who would be the villain?
Also, on Endor, the Ewoks were going to be Wookiees, which wouldn't change everything, but the movie would be different. Ewoks would probably not exist, but things would be very similar.