I played RE 1,2,3 with my cousins. RE Zero, Outbreak, 4,5, and 6 with friends.
Re Rev 1 i played with randoms, and i'll probably do the same for RE rev 2.
I still remember when the PS2 had functioning online play. I actually got a full team of 4 people to play the final mission in Outbreak. But they all quit on me eventually and i failed because i became infected.