It's more dependent on the game you are playing and the GPU you have. However, for gaming right now, 8 Gigs is the sweet spot.
Yes i meant system ram, cheers guys i thought this was the case, its just that another person commented how i would cripple my system at 1440p without 8gb ram. I wasnt so sure about that though. Thanks!
Most games dont come close to using 4gb of ram. Crysis 3 recommends 8gb, but you probably dont need it.