Games such as strategy, sims, and mmo tend to be largely single threaded and cpu limited.
Processing time per turn is reduced when the single thread performance is increased.
I play a lot of civ 2,4, and 5.
I keep a task manager open on a side monitor.
My observation is that I see about 30% busy on each of my 4 cores. That is a I5-7600K@4.9.
Yes, it does take a long time per turn on a big map with lots of elements.