The CTS-V is said to have run the 1/4 mile as fast as email@example.com. That is fast enough to deal with the vast majority of stock displacement S85 V10 out there that are naturally aspirated. It would take Schrick cams and headwork to bridge the gap but the costs start getting pretty high when eeking out those last naturally aspirated ponies. It is not as simple as pulley, tune, and axle-back exhaust like the CTS-V has thanks to its factory boost.
For the outcome to be reversed, the M5 simply needs some boost of its own as in a supercharger. Still, the V10 hangs in quite well. Respect to the CTS-V as well for such high performance with basic mods. No wonder BimmerBoost and the GermanBoost network is seeing an influx of CTS-V owners who are switching from their German sedans.
Thank you to @TZ04XJR for the video.