It depends on your definition of scary. While they do have elements of the supernatural which are often associated with fear, the Marvel touch means there's also a lot of action and heroics. So, while there are spooky moments like a ghostly apparition floating in a dark alley or a haunted mansion scenario, the heroes usually step in to face the threat, which lessens the pure 'scary' factor a bit. For those who are easily spooked by ghosts and the unknown, though, there are definitely parts that can send shivers down your spine.
There are several versions of Ghost Rider in Marvel Comics. It's hard to give an exact number as new iterations and alternate realities can add to the count.
Ghost Spider, also known as Gwen Stacy, has a complex story. She gains spider-like powers and navigates a world full of villains and challenges while trying to balance her normal life.
One interesting story could be about a ghost that haunts an old Avengers base. Maybe it was a former agent who met an untimely death there and now his spirit lingers, causing strange occurrences like lights flickering and objects moving on their own.
If Marvel Comics went metal with Ghost Rider, it'd likely result in a revamped look for him. His bike could be more like a monstrous metal machine, and his flames might have a more metallic sheen. The tone of the comics could become much darker and more rebellious.
The Avengers originated in Marvel Comics. Marvel has developed a vast universe of characters and storylines, and the Avengers are a key part of it. Their adventures have been adapted into various forms of media, including movies and TV shows.