There are isolated instances when the i7 will be better for heavily threaded games that actually benefit from hyper-threading. I have read and seen some semi-convincing evidence that having an i7 improves Crysis 3 minimum frame rates when running on super high-end systems.
But yes, in the majority of scenarios the i5 equals the i7 for gaming. I can say quite confidently you would be happy with either, considering an overclocked i5 can run high end multi-sli / crossfire systems.
The i5 have plenty of juice, there are probably literally 4-5 games on the market that benefit from hyperthreading, and the difference is so minute it's hardly measureable.