It wasn't about the top speed. It was about the fact that the GT-R could accelerate with the 997 up to that 190 mph indicated. If the Porsche has a 0-200 km/h time of 12.8 seconds and the GT-R can keep up, it's pretty safe to say that it does the same thing in around 13 seconds. Now, the Audi does it in 14.9 seconds. That's a difference of 1.9 seconds.
The RS6 runs the 0-60 in 4.4 seconds
according to this page. The GT-R does the same in 3.3 seconds, or 3.6 if you want to say so. The difference is thus 0.8 to 1.1 seconds, depending on the source.
The gap grows, pretty dramatically, as the speed gets higher. Isn't this quite a clear indication that the GT-R is better than the Audi from a roll?