I think there's definitely an illusion of size in videogames - not necessarily for doors and things where you know what height they should be relative to a person, but for things like monsters I tend to think they're smaller than they actually are if you put your character next to them and actually look at the size of them.

I figure it's a disconnect of perspective and you interpret the size of things relative to where you're viewing them from, which is a few metres back from where your character is standing.