Games don't use hyperthreading? say that current games don't utilise more than 4 threads.
@ OP
Imagine four men with two hands each. Now, place BF3 in there. it needs 4 hands. now in case of i5, four person will run BF3 with one hand each. in case of i7, 4 man will run it with a single hand each, too..
but, say, BF4 will utilise 8 threads. then, i7's four men will run it with both their hands while i5's men will run it with a single hand each inspite of having the same power!
I hope I was able to explain it.
I recommend ASRock Extreme4 Gen3 Z68. PCIe 3.0 slots, Ivy Bridge upgradbility, all solid capacitors, easy overclocking.