We already knew that the HTC One M8 technically cheats on benchmark tests much like the Galaxy S4, Note 3, and probably the S5 did. So that's not really news to us. But 3DMark has been delisting devices that cheat on benchmarks so that you can get authentic benchmarking scores. 3DMark has delisted the HTC One M8 from their benchmark rankings because, "The platform may not detect the launch of the benchmark executable. The platform must not...modify the usual functioning of the platform based on the detection of the benchmark."
The HTC One is a pretty powerful device, I mean it does sport the Snapdragon 801 which is a very powerful processor. But in the graph from Anandtech's review of the HTC One M8, you can tell that with the Google Play APK, it does about 15% more work than a regular APK that does the same benchmark. Which means that the HTC One M8 is ramping up it's GPU while running certain apps. Now it's not technically cheating, because the GPU will ramp up anyways for games and heavy lifting anyways, but its still not fair. Which is why we run AnTuTu X here on review devices, as they get the authentic score.
We've been saying this for quite a bit now, but benchmarks shouldn't be the reason why you buy a device. They don't really translate to real-world experience at all. Which is truly what matters. While the Galaxy Note 3 did score higher on AnTuTu than the LG G2, it doesn't mean that the Galaxy Note 3 is a faster or more powerful device than the LG G2 at all. In fact the internals are the same aside from the RAM. 2GB of RAM on the LG G2 and 3GB on the Galaxy Note 3.
So this shouldn't keep you from buying the HTC One M8, because it's still a really great device, and I'd buy one as well.