an i5 is better for most current generation games, because it can execute instructions more efficiently. Clock rates simply represent how many things can be done at once, not how efficiently they're done. Also, AMD 8 cores have 8MB L2 and 8MB L3 cache, which are basically your processor's RAM, and both the L2 and L3 function as the same thing. Intel processors only have 512KB of L2 cache, and most of them have 4-8MB of L3 cache. So basically, the higher the workload is, the better the AMD processor is going to perform compared to the Intel processor. For instance, if you were playing Watch Dogs or BF4, and cranked the render/view distance up to max, you would notice a 10-20 difference in fps between an 8350 and 4770K because it's a huge workload that's optimized for 8 cores, and no matter how efficiently you do a task, it won't matter if you can't keep up with the amount of things that need to be done. Another thing to think about is that with the next generation of gaming, more and more games are going to be optimized for 8 cores, especially with Unreal Engine 4 being introduced. In 1-2 years, the 9590 is probably going to be comparable to the 4960X, simply because it can do more things at once.
Intel: Better for most games now, better when running single-thread applications
AMD:Cheaper, Future proof, better performance with demanding workloads