The new Halloween ignores all the previous sequels, but it almost approached the original film in a very different way as well. It turns out that the original version of the new film's script, written by Danny McBride, Jeff Fradley, and director David Gordon Green, would have essentially rewritten the ending of the original Halloween, and in the process would have killed Dr. Loomis, the psychiatrist played in the original horror classic by Donald Pleasance who finally stops Michael Myers.
In the climax of the original film, Dr. Loomis, who has been following Michael Myers' path of destruction since the beginning of the film, sees a pair of children running from a house in fear. He finds Michael Myers attacking Jamie Lee Curtis' Laurie Strode and shoots Michael multiple times, eventually knocking him off a balcony onto the ground. He speaks briefly with Laurie, before looking back down at the ground and seeing that Michael is gone.
According to Bloody Disgusting, the original opening of the new Halloween would have recreated this sequence, but with some major changes. After Loomis enters the bedroom where Michael and Laurie are, Michael attacks Loomis, causing the doctor to drop his gun. Myers strangles Loomis to death before Laurie picks up the gun and shoots Michael, causing him to fall from the balcony. In the next scene, the police arrive and take Michael into custody.
Apparently, the decision to not include this opening was made at the request of John Carpenter himself, who felt the change would be a mistake that the audience wouldn't like.
All in all, Carpenter was probably right. It's one thing to erase all of the sequels from continuity for the new Halloween, but changing the way the original ended would probably be a bridge too far for fans. If the story is going to be drastically changed then part of the value of making the new movie a sequel in the first place is lost.
Still, it's understandable why the new Halloween might have considered this. Dr. Loomis certainly isn't going to be a major character in the new film, and Jamie Lee Curtis is. The Laurie Strode of the new film is a character that takes action but the one from the original film is little more than a victim. Showing her as a more proactive character in the opening flashback would have better set the stage for the version of the character we see in the new movie.
None of this is to say that Dr. Loomis won't appear in the new Halloween. It's already been reported that the character will be given voice in at least one scene in the movie. More than likely we'll learn what the doctor's ultimate fate was, though it will certainly have happened sometime after the events of the original movie.