There are two types of CPU intensive games that rely heavily on one or two performance critical threads
and will perform best on CPUs with their highest single threaded performance.
99% of games currently in existence.
Games that can leverage Multithreading and will scale more evenly with core counts with predominantly
single threaded games.
The game can be considered CPU intensive when the performance critical part of that thread exceeds the
single threaded performance of what can be considered a mainstream CPU and becomes the dominant bottleneck.
Multithreaded games are much the same, except that the performance critical parts may be more spread
out across threads.
Once any of those threads workload exceeds what the typical mainstream CPU can handle.
With all of the background stuff thrown in, the CPU becomes the bottleneck again.