if the CPU is under stress then thats normal, as for lowering it your options include
desktop
1, installing a better/more fan/fans
2, replacing the thermal compound
3, giving it a breather, playing a game for 6 hours is the computer equivalent of running a marathon
laptop... ehh, you have a lot less options, only thing i can think of is making sure your laptop is only on a flat and solid surface. all of your fans and are on the bottom and if they are covered by squishy things like legs or cushions then they wont get the airflow they need. to much of this kind of behavior can do permanent damage to the motherboard and other components if your not careful