How many people have completed 50 Cent, Damnation, Saints Row 2, H.A.W.X, Red Alert 3 and Too Human, as well as the big hitters like Halo 3 and Gears of War from start to finish in co-op? The bigger titles are guaranteed to have more people playing them, but if you get the chance, try some of the smaller titles out.
Running naked together with only a cone on your head is surprisingly wholesome (c.f. Saints Row 2), and every game should have a profanity button (a la 50 Cent!). Discovering moments like this with someone else adds so much more to a gaming experience, moments that you may never come across in the more "co-opular" games. Throw in some great level design and you may have found an instant classic.
So next time you pick up a copy of that monster hit that everyone wants; remember the bargain bin and share some of that co-opularity around. Pick up two copies of a game for £5/$9 each and give one to your friend, you never know you may find a hidden gem (and even make a profit through trade in!).
What are some of your favourite moments from the less co-opular games you have played?
Has co-opularity ever affected your co-op gaming experiences?