Antonyms for the phrase "most out of this world" include the words ordinary, conventional, typical, normal, and mundane. When we describe something as out of this world, we often mean that it is exceptional, astonishing, extraordinary or exceptional. The opposite, therefore, would be rather plain and unremarkable. For instance, a standard office job with regular hours and little variation in responsibilities could be considered mundane in comparison to a career as an astronaut, traveling to space and exploration. While one may be considered a daily chore, the other promises to be an adventure that's out of this world.