The main character is the man with the lamp, of course.
In the 'a man with a lamp story', the man with the lamp is the main character. All the events and the message of the story are likely to be related to his actions, his journey with the lamp, and perhaps what he does with the light that the lamp provides. He is the one that catches our attention and through whom the story unfolds.
It could be that the 'lamp man' is a mysterious figure. Maybe he's not really a man in the normal sense, but more of a spirit or an entity that inhabits lamps. In this case, he would be the main character who causes strange things to happen around the lamps. For example, he might make the lamps flicker at certain times to send messages or warnings to the people around them.
The main character is the man with the lamp, of course.
There are two main characters in the man and lamp story. One is the man, who is probably the focus of the story's action or experience. The other is the lamp, which must play an important role in the man's life, maybe as a source of light, comfort or even as a symbol for something more profound in the context of the story.
In the blind man with a lamp story, the most important character is clearly the blind man. He is central to the story as he is the one performing the action of carrying the lamp. There may be other people in the story who interact with him, like those who might be walking around and are affected by his lamp - holding, but the blind man is the main focus.
As I don't know the story well, I assume the old man is one of the main characters. And perhaps there could be other characters like the people he meets while his story with the lamp unfolds during Christmas, like his neighbors or family members.
A curious child might be the main character. They find the broken lamp in their grandparents' house and start to imagine all sorts of stories about it. They might try to fix it with their limited tools and knowledge, getting into all sorts of cute and innocent mishaps along the way.
I don't know the 'the lamp story', so I can't say who the main characters are. Maybe it's a story about a lonely old man and his precious lamp.
As we don't know the details of 'the man story', the main character is simply 'the man' in question.
Since I don't know the exact 'old lamp story', I can't say for sure. It could be an old man who owns the lamp, or a young adventurer who finds the lamp.
Since I don't know the exact 'lamppost man story', the main character is probably the man who is associated with the lamppost in some way.