Told moobaa last week that I'd noticed my first plays of SG revolved around using pods to jump to extend the Powerzone, more than just shooting stuff, so went for the PP achievement to try to train myself out of the habit.
Space Giraffe - Player's views, help needed, etc.
It's plausible that Space Geoff taxes the CPUs more than those games and therefore you notice the overheating problem more.
Now I know everything you're saying makes sense but I've played GOW for over four hours in one session before and I know I've put in three to four hours on VT3 and Geometry Wars solid and it's never overheated. Go figure.
Overheating is a common problem among the older Xbox360s. the Heatsink and fan they equipped it with is not quite up to the job and the thermal glue its held on with has a tendancy to melt.
If you send it back to MS they will glue a new HSF on for you, but probably take 6 weeks to get it back
Best bet is to part exchange it for an elite
They're MUCH quieter than the original noisemonster and cooler too.