Results: Far Cry 5 and Forza Motorsport 7
Far Cry 5 (DX11)
A similar situation plays out in Far Cry 5 at 2560x1440: GeForce RTX 2080 is a little faster than GeForce GTX 1080 Ti, but not enough to warrant its price premium.
Efforts to make the comparison between RTX 2080 and GTX 1080 fall apart when we take price into consideration. Really, this is a battle between TU104 and GP102.
Even at 4K, GeForce RTX 2080 is less than 10% faster than GTX 1080 Ti after spending almost 15% more on the Founders Edition card.
Forza Motorsport 7 (DX12)
Both GeForce RTX boards really take off in Forza. The 2080 posts a 28%-higher average frame rate than GeForce GTX 1080 Ti, at the same time beating GeForce GTX 1080 by 40%.
That 40% advantage compared to GTX 1080 carries over to 3840x2160. Really, though, all of these cards deliver playable frame rates at 4K.