At the moment is better to have less, but more powerful cores than having many of them less powerful individually. That's why in many games i3 cores surpass the AMD FX 8350.
The best price/performance ratio you can find is an i5 6500-6600-6600K. It has 4 cores and the four of them are powerful enough to move all modern games, without being a bottleneck for powerful GPUs.
In the future? Things tend to the multi-core path. But today, having more than 4 cores it's not really useful.