I was just typing an answer to the post asking “With MCC on PC, is there any point to XBox now?” when it got locked. But I think I made a good list of reasons for XBox Gaming, so I’m going to post it anyway.
Of course, for a start, MCC, Reach and Halo 5 can be all be played on XBox One right now (!), but MCC and Reach will take time to arrive on PC, and though presumably Halo 5 will follow, that’s not confirmed yet. But even after they do arrive on PC, consider these ideas which apply to different groups of Gamers:
(1) PC Gaming at a desk with KB/M is a different experience from sitting on a sofa to do Console Gaming on a TV with a Controller. Some prefer one, some the other, some do both.
(2) Console Gaming with 2-4 player splitscreen round a large TV is also different from what you can do on PC.
(3) Console hardware is far cheaper than a decent Gaming PC and increasingly even an entry level one. If someone only plays Campaigns and Campaign-only games and not Multiplayers, they don’t need the extra expenses of XBox Live, making it the cheapest way to play mainstream AAA title Campaigns. The price of a One X ($500 or less) would only buy a basic entry level Gaming PC for many new titles. Meanwhile, 4K Halo MCC (now with Reach incoming), 4K Halo 5 and 4K Halo Infinite can be played on a One X which costs less than $500/£450. A 4K capable PC that could play 4K/60fps Halo 5 Forge for PC costs 3-4 times the price or more ($1500 - $2000+).
(4) Most PC games don’t release on DVD or Blue Ray disc any more, are download only, and require anywhere from 3GB (Ori) to 100+ GB downloads (Forza 7). Many people don’t have unlimited or superfast internet plans, so being able to buy an XBox game on disc is great (including many games for One X that have the Campaign in 4K HDR on the disc, such as Shadow of The Tomb Raider, Assassin’s Creed :Rogue Remastered and Hellblade: Senua’s Sacrifice to name a few).
(5) Apex Legends can be played at 60 fps on XBox One (OG, S and X, though the S could do with a performance improving update). But the PC version requires a 3.8 GHz capable quad core processor that Steam’s Hardware Survey suggests only a third or so of PC Gamers have, and that’s the minimum even just to play the game, then a $279 GTX 970 graphics card or above to play it at 60fps (970 is 3.5 TFLOPS, just below PS4 Pro at 4.2 TFLOPS)! Seems the XBox One, even the OG, isn’t quite so “underpowered” as some claim, as it can do AL at 60fps!
(6) Consoles are far more portable for visiting friends with, or going to LAN Parties.
(7) Perhaps related to (1), last but not least, a sofa is often sooo much comfier than even a good PC Gaming Chair, LOL! 
So, yes, I predict there will be continued demand for XBoxes, Playstations and Switches. It’s a different experience from PC Gaming at a desk with Keyboard and Mouse, can be a lot cheaper, has discs still, 2-4 player splitscreen, are consoles are more portable.
Finally, whatever graphics power it is, someone’s Gaming Rig (Console or PC) is often their “pride and joy”, and for people on lower incomes (i.e.most people) may have taken a long time to save up for it, so it’s not nice to insult it. But I have a saying for when someone claims your Console or PC is “underpowered” - just reply “Don’t rag on my Rig, man!” 
What do you think? Any more good reasons for XBox Gaming I’ve missed?