Man of Honour
Well in Rage 2, a game that released last week the 2080ti is 50% faster than the 1080ti at 4k, so the "30% at best" line that trolls like to use is a flat out lie
The 30% figure that often gets used is just a rough average and if anything is slightly too high as I have seen the difference as low as about 12%, it all depends on the software but 30% is a reasonable average..
So yes you can get the odd game title that will run 50% faster.