Boderlands is 4 player co-op I believe? Although I haven't tried it as it doesn't look my cup of tea some people really love it.
Play this: http://team.forsvarsmakten.se/english/
Pretty fun co-op. Could even be fun against other ocuk'ers.
Ta, I'll check it out! What sort of game is it?
Memory puzzles!
Oh! I assume you're kidding?
if you like rts games then you could try supcom forged alliance ...survival maps
Sins Of A Solar Empire ? can be played co-op or versus with AI over massive maps, has elements of epic space battles, pirates , diplomacy, research, colonization of new planets, you can back stab your friends and more importantly it can also be saved at any point - truly superb game which can be tailored to however you want ...
Play this: http://team.forsvarsmakten.se/english/
Pretty fun co-op. Could even be fun against other ocuk'ers.
And it's the kind of game that lends itself to playing 4-5 player co-op? (rather than vs?)