resolution is also a big factor in how the cpu does. tom's did a comparison recently and saw a dual core pentium keeping up with an i7 at 4k. gpu is so bogged down at that resolution that the dual core keeps it fed easily.
but obviously at 1080p, the gpu can do more and the dual core quickly shows it weakness as the i7 pulled away by a very long shot. so lot's more to consider than just cpu itself. what resolutions? gpu paired with it? specific game being played? and so on and so on.
the i3 is a solid all around choice and won't leave you begging for more on most games. if that's good enough for you, then it's all yu need to buy. if you want to push everything to the max and never compromise on anything, then the most cpu power you...