They're mostly jumpscares, yeah.
>blocky sector forest
>single spooky oogabooga is let loose and you gotta git him without gitting got by him
>he's fast and he's made from a photo of a Halloween mask, he's also obnoxiously loud
>quality and presentation improves with each entry, but the concept stays the same
>third has you fight a whole bunch of different ghoulies in sequence, like a boss rush
>final boss is cut out of a video clip of The Ring, need to time your shitty bow and arrow so she doesn't screamer you to death
Ghoul's Forest was heavily inspired by the Commodore 64 game The Forbidden Forest (which is a pretty impressive game for that hardware), and Ghoul's Forest 3 best mirrors it with the whole bow and arrow thing, stages of different creatures, and the "Yurei"' demanding the right timing and reflexes like the Demogorgon does.
Someone also made a fan map of GF3 named Torn City, which was specifically made for playing with Skulltag in multiplayer, the setting being an abandoned city in a black void with a huge gaping crevice dividing it up. Torn City lacked the Yurei, you'd just be faced off with Juggaloface, Biggie Skulls, and Anorexic Loper all at once.
Ghoul's Vs Humans was a bit of a different animal because now you got to play as the creepy crawlies and oogabooga people yourself, and it was pretty popular for a while. One of the memorable exploits was where you played as the Creeper Ghoul, and you were meant to be a little hard to see, but if you crouched, his sprite compresses vertically and his already short hitbox becomes almost flat, so you could legit lay in wait and hide behind the step in a staircase and someone coming down could not see you at all.
The intended premise with the Creeper was that he was supposed to skulk around and camp, I'm pretty sure, since he was frail and not too fast, and you had to look out for him (and his ranged attack which slowed you down so he could chase you), but the crouching got patched out lol.