Well if you're going to play multiplayer, then you should look into a cheap AMD motherboard and either a FX 8120 or a FX 6300.
If i remember correctly Battlefield 3 was the only game capable of utilizing 8 cores, which made AMD's FX 8 cores perform as well or better than Intel's Core i5's.
But if you do care about your electricity bill, then Intel is the obvious choice.Just make sure you don't buy a Core i3 since you'll realy feel the two cores struggling in multiplayer.