The faster loading times from Xbox One X may be its most important advantage

While the main selling point of the Xbox One X is the ability to showcase games in native 4K and HDR there are several other benefits that will be seen by playing games on the new more powerful system. Focusing just on the loading time improvements they are significant, given the number of times a game is loaded up and into over the course of its lifespan. 

Madden NFL 18
Boot to Main Menu: Xbox One (68 seconds) vs Xbox One X (51 seconds). Cut by 25%
Load into full game first action: XB1 (70 sec) vs XB1 X (26 sec). Cut by 63%
Load into Franchise training games: XB1 (49 sec) vs XB1 X (20 sec). Cut by 59%
Load into Practice mode: XB1 (61 sec) vs XB1 X (20 sec). Cut by 67%
Also save a few seconds loading into Ultimate Team, Franchise, Longshot.

FIFA 18
Boot to Main Menu: XB1 (79 sec) vs XB1 X (56 sec). Cut by 29%
Load into full game first action: XB1 (34 sec) vs XB1 X (14 sec). Cut by 59%
Also save a few seconds loading into Ultimate Team, Journey, Skill Games.

NBA 2K18
Boot to Main Menu: XB1 (34 sec) vs XB1 X (32 sec). Cut by 6%
Load into full game first action: XB1 (67 sec) vs XB1 X (39 sec). Cut by 42%
Also save a few seconds loading into MyCareer, MyGM/MyLeague, MyTeam, Shootarounds.

Forza
Boot to open world racing in Forza Horizon 3: XB1 (170 sec) vs XB1 X (99 sec). Cut by 42%
Boot to Main Menu in Forza Motorsport 7: XB1 (60 sec) vs XB1 X (46 sec). Cut by 23%
Menu to Career to race first action in Forza 7: XB1 (94 sec) vs XB1 X (68 sec). Cut by 28%

All games should see some improvement to loading times. Install times on the other hand have been extended on the Xbox One X by about 35% (.5GB a minute vs .7GB a min on regular Xbox One). Some images captured from the games in 4K/HDR can be viewed here. A full early assessment of sports games on the Xbox One X will be up later today written for Sporting News.