Inspired by some discussions on a writing forum.
Prologues can work, but I feel they’re very much overused. For them to work, they need to be something from the history of the main character in the story (which is probably better handled when it becomes relevant to the story rather than as a prologue), or obviously something that doesn’t include the main characters of the story, and the events have to become important later. The prologues I hate are included solely because the writer isn’t good enough to build the exposition into the story, or they’re back story with some interesting characters who I expect to be part of the main story and then they disappear at the end of the prologue.
Good examples of prologues, for example, would be many of Clive Cussler’s books where the prologue is usually years in the past, it clearly doesn’t involve the main characters of the novel, it will become important later if not the driving force for the plot, and it’s an interesting story in its own right. Bad examples would be many of the unpublished novels I’ve critiqued over the last few years.