I was playing zombie takeover for about 30minutes and then Facebook, safari and messaging quite a lot but I wouldn't of thought that would cause it to get as hot as it does.
I don't leave any apps open, soon as I'm finished doing what I need to do I close them down.
I suppose it's normal for it to get hot while charging aswell?
Games will get the phone quite warm as with anyphone also charging will also warm the phone a little.