What CPU core temp are you seeing when the CPU is under heavy load and ready to shut down? You need to use an applet that properly reads the FX CPU core temp as many applets read the CPU socket temp instead of the CPU core temp. Programs like "Core Temp" tend to be pretty good at reading AMD processor temps. There are also other software applets that can properly read the FX CPUs too. Have you checked to make sure the thermal material between the CPU and heatsink fan is good and the HSF is properly mounted? Have you checked your PSU 12v rail power to the mobo under heavy gaming to make sure it is remaining at or above 12v? It's also worth un-cabling and re-attaching all of the cables just to make sure that you have solid electrical connections.
FWIW, different games impose different CPU and GPU processor loads. That might account for different thermal loads on the CPU.