Ive found that any tablet with a high resolution screen the devicel get really warm with playing graphic intensive games. There are several issues here. One is passive cooling. These devices don't have fans. Next is high res screen. That means lots of pixels to turn on. Next is graphics processor. Games run this hard, which means more heat. You can even tell where the chip is inside as you can feel the spot is warmer than others. Also, most of the devices have larger batteries and they get warm when you draw lots of power from them.
Heck, the nexus 10 will throttle down its speed if you let the device get too warm. IPads don't do this, in my experience.
Ipad mini and iPad 2 dont have these issues.