Zombies stop being scary after the first few games back in the day (resident evil 2, resident evil remake)
Meh, I don't know. Demons are just monsters to me, no more scary than Gears' Locust. Put them in a possession movie and that's unnerving, but usually only because those films put children at risk, usually young girls.
"'Grab the guns!' 'What about the troll?' 'Leave the troll.'"--ATHF