It depends if you have your heart set on AMD or Intel.
To me it sounds like you've made up your mind on a Ryzen CPU which is a fine choice(something I would have never said a year ago about AMD).
What is your budget? What do you do with the PC? A 1080ti is quite a powerful card and should be paired with a powerful CPU.
Personally I would go for the 1600x 1700x or, even 1800x.