I don't disagree that it
does play games. That would be silly. But it's not "great" for gaming. Again, I suppose that's subjective.
The 5K iMac I purchased did
NOT provide a significant performance boost over my 2010 iMac when it came to gaming. It was an improvement, but not 5 years of improvement. Not even close. The machine was
significantly louder, the GPU ran at 108C (and reached that temperature in a few seconds) which is above the suggested upper thermal limit of the M295/395X cards, and it suffered from thermal throttling. All of those things point heavily towards a machine that is being used for something it is absolutely not intended for. All of those things are common on all max-spec 5K iMacs.
You can watch a video with more details about this. And
another showing the GPU reaching mad temperatures in a few seconds and starting to thermal throttle. Not even full screen gaming.
iStat Menus and GPU-Z are two of the very tools that have been used to show the thermal issues.
I'm confident the iMac will see a redesign soon enough. It's starting to age now with an almost identical design for nearly 6 years - slightly thinner edges for the past 3. Hopefully that will come with an improved cooling system than this one designed for hardware from 2012. The compromises made for thinner design are now very apparent. That said, Apple seems to like relying on thermal throttling. The new MacBook literally relies solely on it at times!
But for casual gaming...yep, it works.