Cooling is pretty simple - cool air in and hot air out. So a lot depends on the position of the laptop while you are gaming. If it's on your lap you are probably restricting the input air to the vents on the bottom. Try it on a table or desk. The hot air also needs to get out so try opening the CD/DVD drive to allow to escape more easily and take your temperature readings again.
If any of that helps you might also do better on a table or desk with something under each end which elevates the vents on the bottom to allow easier air flow into the vents. Just be sure not to block the vents with whatever you put under it.
If none of that is sufficient you'll need a cooling device. Look
here to see what is generally available. An active laptop cooler with fans will give best results. The fans can be powered from an external power source or using a USB port. Using the USB port will add a small amount of heat but the fans will handle that and more. It also occupies a USB port so you may not have enough ports depending on what you have attached. Make sure you do your research. It's possible a badly built/configured cooling device won't help at all so get a good quality device.