Quite normal. The Intel processors used in Macs are designed to automatically shut down to prevent damage if they truly overheat (around 100C/212F - 105C/221F, depending on your processor). iStat Pro will give you accurate readings of your temps, among other things.My iMac is extremely Hot behind the camera when i play games... is this normal???
About this though, I'm wondering, does this increase the intake of dust too from the open air flow?As a minimum DIY "venting improvement" task, simply remove the underbelly memory cover (3 x simple screws). One doesn't see this underbelly cover anyway. Removing this cover allows more air flow into its underbelly - which helps cool its insides as well.