GHOST: No. Most vengeful ghosts are drawn to certain people in particular or associations with certain areas. Their vengefulness is usually limited, so the passerby doesn't even have to care.
ZOMBIES: Yes. Giant armies of zombies, showing the inhumanity of humanity is always freaky. Not because they look bad, but because they eat people and infect and some of them are actually fast. Everyone gives a damn about zombie hordes or we all die.
MUTANTS/MONSTERS: Not as scary as zombies, though there is a scare-factor. Thing about mutants and monsters is that the average person's a little desensitized towards outright horror-creatures. And unless explicitly said, they don't spread like zombies or have great numbers.
DOLLS: NO. No, no, no, no, no. First, I didn't like FF4 that much, so you get super bury-the-needle NO. Second...Chuckie and company are only as scary as real serial killers, because they're serial killers. Dolls are, however, not nearly as strong or as powerful as anything else here, including the clown.
CLOWNS: And I stop for a second, because I've seen Killer Klowns from Outer Space. But barring them, clowns are only scary to people afraid of clowns (the marked phobia). Either that or Pennywise, but he's clearly a monster.
A MURDERER: Can be very scary. Not as much as zombies, though, for obvious reasons.
ALIENS: Not as much as you'd think. Since we're not specifying the type, we can say that not all aliens are made of kill-you. And if they are, it may be about as scary as war, but not the horror of "I'm afraid to pass gas because a zombie will hear me.".
So, zombies win.
