Yeah, this is exactly why I ignore the sequels in general, aside from Halloween III.Rewatched Halloween (1978) and Halloween II (1981) last night.
Watching them back to back for the first time I really appreciated just how different they are from each other, and how much better the first movie is (even ignoring the infamous sibling twist).
Friday the 13th had come out in between, and just as that movie was copying Halloween, Halloween II now got to copy Friday the 13th. The sequel is notably bloodier. You barely see any blood in the first movie. At most it suddenly shows up as makeup on an actor. The sequel kicks off with blood bursting from a stab wound and a poor kid mumbling incoherently with a nasty razor lodged in his mouth. By the end so much blood is literally pooling on the floor characters are slipping in it. And the kills are more roundabout and vicious as well, Friday the 13th style. In the original Michael merely strangles two girls from behind and pins that guy to the wall. Here he uses a variety of different impromptu methods - claw hammer to the head, syringe to the eyeball, strap down and bleed someone to death with a tube, boil a chick's face off in a hot tub - with highly detailed, nasty results. We're also now doing car crashes and explosions too. Gotta up the ante.
I don't know what it is about bad directing that turns every character in a movie into an asshole or a smartass, but this movie definitely caught that virus. So everyone who isn't Laurie Strode in H2 is behaving like a complete douchebag: dismissive, short tempered, trying to one up the other person with dumb sarcasm all the time. Suddenly Haddonfield isn't the drowsy, peaceful, nondescript town from the first movie. It has 1980s grime and filth all over it, and is populated by nasty or ridiculous characters who belong exclusively to a horror movie.
Some final observations.
1. In the opening recap of H2, which mixes archive footage with new stuff, Loomis fires SEVEN shots instead of the six he clearly fired earlier (and which he keeps mentioning as well). That just grinds my gears.
2. The sister twist doesn't meld that well with Michael's actions in the first movie. If his sole purpose is to kill his "other" sister, why follow around Tommy in H1? Why bother killing the three other kids at the Wallace's house? Why steal Judith's gravestone and prop it by Annie's dead body, wouldn't he save the display for his actual sister?
3. Where are Laurie's parents? We see the dad drive away at the beginning of H1. In H2 the head nurse tells Laurie they can't reach her parents (ok, so she has a mom too) as they're not home nor at the party they were attending. By the end of H2 they're still missing.
4. Back to the sister twist... it doesn't add anything to the story, other than to explain why Michael is after Laurie. Frankly he kills so many people at the hospital it might as well just be a coincidence. Laurie has a dream about meeting a young Michael but makes nothing of it; by the end she's still unaware that Michael is his brother, just as she was still unaware by the end of H1 that "the bogeyman" she fought off was the infamous Michael Myers.
5. In the first two movies, which take over the course of a couple of days, he gets: stabbed in the neck with a knitting needle, stabbed in the eye with a clay hanger, stabbed in the chest with a butcher knife, shot 6 times in the chest with a revolver, falls form a second floor to the ground, boils his right hand in 140 degree water, gets shot another 5 times in the chest, gets shot another 2 times in the head (effectively blinding him as blood gushes from both eyes), is at the dead center of a gas explosion and eventually burns alive. He somehow survives all this and wakes up from a coma several years later like nothing happened.
(H2 introduces Samhain but it's not until the sixth movie that we finally establish Michael as a supernatural force.)
6. Loomis gets a bad rep as the guy somehow responsible for Michael breaking out and going on a killing spree. I blame Marion Chambers, who thinks it's a good idea to park your car by a herd of escaped crazies and roll down your window when one of them climbs on the top of your car. Later she shows up in H2 to recall Loomis, who is actively trying to stop the spree and kill Michael - which he achieves, basically, at least until H4 happened.