Halo 4 and 5's campaigns have been nowhere near the calibre of Sony's blockbuster single-player only games like God of War, Horizon Zero Dawn, Spider-Man, etc. Even just comparing scope to this year's Death Stranding and Days Gone - the Halo campaigns are like 10 hours. Sony's games are often 2 or 3 times longer and obviously a lot more acclaimed too in the case of their many GOTY winners and nominees over the past 10 years.
Gears 5 was a step in the right direction, but its campaign still wasn't anything special and wasn't very long either. The difference for single player fans is that Sony's games feel like large, impactful, filling experiences. Most of Microsoft's games have a single player campaign that just feels like a fun romp but that's about it.
I hear you. Even though I don't own a PS4, I can't deny that I'm a little jelly of games like Uncharted 4, TLOU2, God of War, Spidey. I love that they take a long time to finish (for me U4 didn't drag, I really loved it all the way) and ND already said TLOU2 will be a long ass game.
I bet Ghost won't be short either. For a very long time I've been wishing to get this on Xbox, a singleplayer experience that is long and great. The open world RPG by Playground in the future? That is definitely going to be something that can be filed under "long" titles and perhaps whatever The Initiative is working on? We can only guess.
NT's next game is probably like Hellblade, can't go expecting 20+ hours from that, but maybe some day they can make something like Enslaved again or DmC. But on a bigger scale maybe.
When I played through all the Halo games, especially 1 and 2, those felt like the perfect length to me. They never felt short to me and I really hope Infinite's campaign is full of epic moments and lasts long too. It's been said before but if TC is open to making something else than Gears (assuming they can, I don't know, I mean the name of the dev says it all it's Gears) that would be awesome. Have a great and long SP with maybe MP as well. Because, look at ND, they made two Uncharted games, then decided to try something else and boy what a game it was.
I cannot forget about Obsidian though, because it wouldn't surprise me if their next big game will be either a sequel to TOW or something similar. Those aren't short games either. But it seems like you would want a long action adventure from XGS, and I can only say, me too.