Go for an i5 as far as gaming is concerned ,any quad core cpu gives you the performance.
http://www.techspot.com/review/734-battlefield-4-benchmarks/page6.html
http://www.techspot.com/review/878-metro-redux-benchmarks/page4.html
See the benchmarks here ,they give a clear indication.Go for an i7 only if you are into video editing and other intensive stuff.They are virtually the same chip with the i5 sometimes being faster in single threaded applications which most are .The i7 is only faster in multi threaded applications which very few games utilize and even then the difference is not discernible.