Wait, Settlers is a long strategy game? It takes less time to play than most of the games named above.

I always emphasize about Settlers that the board is mostly a distraction: it's really a game about reasoning about asymmetric resource distribution, and figuring out how to value resources more accurately than your opponents given that they don't want you to know how much the resources are worth to them.

So far the Coop game I've most enjoyed is Forbidden Island. This is the San Juan to Pandemic's Race for the Galaxy: simpler mechanics, faster play. I'm beginning to think that you need fast play to keep coop games viable. As soon as there's time for someone to micro-optimize the game each turn, given the crowds we move in somebody will. The micro-optimizer becomes the de facto solitaire player (at least until two micro-optimizers start arguing).

Space Alert solves this by eliminating analysis / communication time. But games with imposed time pressure have their own problems (and desireearmfeldt won't play them at all).

Maybe something like Res Publica would work: a game where player communication has to occur in a very stylized fashion. Another great game of figuring out the values of resources to other players, a bit like the Bohnanza games in reverse.