Multi-core use in game engines is till pretty woeful if you ask me and largely because the game needs to have discrete processes/threads that can be assigned to cores rather than essentially timeslicing a single thread across cores. A lot of game engines haven't really needed to go "properly" multi-threaded, because they don't "do a lot" on the CPU vs. the GPU and higher clock speeds is therefore more important to keep feeding the GPU pipeline.
Sims are generally different, as they tend to have a lot of AI, an intensive cockpit environment, a BGS, a procedural engine creating sky boxes (ED) or a dynamic campaign (Falcon 4

) and their engines (especially the latter) have been written from the ground up to take advantage of multi-core environments. VU2 for Falcon4 was way ahead of its time as they started development in 1993 with this stuff built in and I suspect COBRA is similar. CryEngine however is the opposite and whilst some elements of it are "useful", trying to retro leverage multi-cores is a world of pain, as CIG are finding out.
Personally I partially blame Carmack, who was banging on about higher clocked single cores being the way forward in the late 2000's - he was/is wrong, but a lot of developers take what he says in the same way as tablets from Moses...