I think GeForce Titan XP 12GB
(Pascal, April-6-2017) is not faster than 2080Ti, it should be on par or slightly below RTX 2080
GeForce Titan RTX 24GB
GeForce Titan V 12GB
GeForce RTX 2080 Ti 11GB
GeForce RTX 2080 Super 8GB
GeForce RTX 2080 8GB - GeForce Titan XP 12GB
GeForce RTX 2070 Super 8GB
GeForce GTX 1080 Ti 11GB
-techpowerup; see Relative Performance chart (GTX 1080Ti 93%, RTX 2070 Super 94 %, Titan Xp 100%, RTX 2080 100%, RTX 2080 Super 106%, RTX 2080 Ti 117%; based on 1080p)
-many benchmark on youtube shows the similarity
However the Titan V vs 2080Ti
which better in gaming is still inconsistent and questionable.
From what I can see from some youtube benchmarks perspective; Titan V can be a lot slower than 2080Ti in some games, but can run better in some too,
The 2080ti looks more favorable to be faster in general.
But on techpowerup the relative performances in-short are; 2080Ti at 96% and Titan v at 100% https://www.techpowerup.com/gpu-specs/titan-v.c3051