Re: "as fast as the fastest PCs."
Intel have a huge budget to work on improved Core and Xeon CPUs (don't forget, they share the same architecture, and business users would snap a significantly improved version up). If they could throw 100% more transistors at the design and make each core even 20% faster then they would do it in a heartbeat. They have AMD breathing down their necks, and AMD are getting close to the same performance per clock cycle. The limiting factor for single threaded performance is clock speed (diminishing returns have long since cut in over improving the design logic), and the max clock speed hasn't changed much over the last three or four process sizes. Yes, you can make the chips go faster, but at the cost of serious heat.
The reason that an i5 is the recommended CPU for gaming is that the single threaded performance doesn't get much faster the higher you go up the range. Most games offload a huge amount of the work to the GPU, but then modern GPUs are very highly parallel so it's not a like-for-like comparison. Game writers work within the limits of what is available, and what their target audience can afford to buy. Most games therefore include a quality configuration setting that adds or removes eye candy, trading against CPU/GPU performance. Try your i5 at 4K extreme settings.