This comic by Saturday Morning Breakfast Cereal pretty much nails Facebook games. It reminds me of Cow Clicker – which was designed to be a parody of shallow Facebook games, but ended up becoming inexplicably popular.
To be fair to Facebook games, one of the reasons I never got into MMOs is because they seemed like complex versions of this same story: “What does a higher level get me? Better weapons and tougher baddies.”