Bad college essays tell stories that the writer hopes will sound impressive, not stories that the student actually cares about. They usually include sentences the writer would never say to a friend.
What football player would ever tell a teammate, "Football has taught me important lessons about hard work and commitment"?
What kid who volunteers at a soup kitchen would ever say, "As I handed the bowl of soup to the elderly woman, I had an epiphany about the value of helping people"?
What student comes back from a trip to Europe and tells her friends, "I expanded my cultural horizons by learning to appreciate the subtle yet important differences between the French and Americans"?
Bad college essays just try too hard, not unlike how Matt Damon (who went to Harvard, by the way) describes bad acting in the first 50 seconds of this clip.