I had to go with Science Fiction because most of my favorite shows, movies, and books fall under this genre. There are endless possibilities in terms of settings and characters you wish to introduce. Almost anything goes in science fiction. The genre itself varies quite a bit. For example many Stephen King stories could be considered mysteries in an otherwise completely normal world if not for one supernatural element making it fit into the science fiction genre. Or, as with Star Trek, the entire essence of the world and the characters within it could be sci-fi. I will use a Stephen King novel and a Star Trek series as my examples to illustrate this point.
A science fiction book I read recently and enjoyed was 11/22/63 by Stephen King. Act one/thesis: Jake Epping is just a normal high school teacher. He is shown a portal to the future by his dying friend. This friend convinces Jake to go back in time and stop Kennedy from being assassinated. Act 2/Antitheses: Jake is thrust into the past and goes though many emotional and physical trials and tribulations in the quest to save Kennedy. Act 3/Synthesis: Jake learns the intricacies of the universe and time travel and what should not be messed with, both worlds come together in the conclusion.
A classic example of the sci-fi genre is Star Trek. I’ll use the series Voyager because it’s easiest to fit into 3 acts. Act one: The crew of the voyager is going on a mission that is supposed to take another ships crew in as prisoners. Act 2: They are thrust though a worm hole or something (it’s been a while since I’ve seen it) and get stuck in the delta quadrant which is unexplored and 70,000 light-years from Earth (which is a reeaaaly long way away). The crews must join forces and work together to make it home. Act 3: The crews befriend each other and have many adventures and losses. They make it home with each character having drastically grown and changed by the end by their long journey though space.
Both stories have the character in fairly normal settings in the beginning. They are then thrust into completely new and unfamiliar settings in which they are stuck. The journeys both take many years to complete with the characters being completely transformed by the conclusion. If I chose Science Fiction as my genre I’ll go for something less serious as I enjoy humor quite a bit as well.