(I'm somewhat breaking my promise to do these in order here, but the next couple of games in the queue deserve a meatier review than I can give them at the moment, so I'll quickly hit this one.)
5 Differences' creator describes it as "more of an art project than a game," and I would be hard-pressed to disagree. The premise of the game is very simple: find the 5 differences between the two panels. Just click on a difference, and it'll be flagged.
If Drone Wars is an example of a game hampered by its medium, 5 Differences is an example of a game which exploits the advantages of Flash. There are a few small touches which set it aside from the equivalent in a newspaper. While there is no interface to speak of, there always is an indication, usually cleverly included in the environment, of how many differences remain to be found. Little touches of animation enliven the scene. And perhaps most interestingly, the five differences aren't always the same -- a replay reveals that they do, in fact, seem to be selected from a larger set of possible differences, giving the game at least a tiny bit of replay value. It also helps that when you click a difference, it disappears, helping you to find other differences without having to remember if you've already found that one.
The real star of this game, though, is of course the art. The scenes are well-drawn, and tend towards the surrealistic and whimsical, providing an entertaining backdrop for your task. The complete lack of an interface is somewhat frustrating -- you can't replay an arbitrary level without starting all over again from the beginning, and there's no save or anything, so you'd better be able to finish this all in one sitting, but it should be an enjoyable and relaxing sitting.