Is MacBook Pro warming during gaming normal?
Yes. That's normal. As for "okay" -- it depends. The heat is coming from the extra graphic activity and CPU activity you're asking your machine to perform when playing the games. The MBPro is vented at the back, along the hinge between the screen and the keyboard, you want to make sure that area is free of obstructions and the hot air can leave escape unimpeded. Long-term exposure to high operating temperatures can certainly be detrimental to the components in your machine. But for the most part, if your machine's venting is unobstructed, it should be able to cool itself adequately.