This thread is a good idea! Great job with it so far!
Also, Ninety-Nine Nights II and Kingdom Under fire: Circle of Doom both are retail games with online co-op. Ninety-Nine Nights has co-op for two people and Kingdom Under Fire has co-op for four people. All players can get achievements for both games.
Also, Guitar Hero II has two player local co-op. I think both players can get the achievements but I'm not sure.