Best bet for an overall list with good info is here:
https://en.wikipedia.org/wiki/List_of_Xbox_One_X_enhanced_games
Tons of games are true 4k. I personally wish they would more often use checkerboard or dynamic to get the framerates up or more stable, but then on my setup I can't tell the difference from 1440p when things are in motion, so I guess I'm not very picky about ultra fidelity.
I have a 1070ti in my desktop, which is an i7 8700 with 32gb ram. There are still times when Xbox is the better place to play a game, whether from perfected optimization on console, limitations of the PC port to properly optimize settings, a preferable player pool online, etc. The most consistent benefit on PC is fast load times. Console hard drives and CPUs barely manage at getting all these high-end assets out in a timely manner.
Often it is difficult to get my PC to do 4k well because the stages of variance for game assets in settings aren't good enough. PC game assets are generally future-proofed, so high settings will have crazy shadows, DoF, AO, whatever that boost the framebuffer too high to work well at 4k, but if I drop them down in settings it will look worse than console. If I had greater control over things like individual post-process levels and detail mesh distances and such I could work it out, but then it'd still be a pain in the ass to set up. So it can often be better to just go 1440p for a smooth 60fps than dick around in settings and ini files.
Consoles can in some cases take this headache away from you and offer something great. Stuff like BLOPS4 for example, is perfectly fine in every way. However, other times you'll get something like Sea of Thieves insisting to be 4k and running at like 15fps in many areas (this was at launch, don't know if it has improved) and compared to that some quick priority decisions in PC settings just gives you a massively better experience. That said, if you're fine with 30fps if you get 4k in return, One X gives that guarantee very often.