No Man's Sky has massive scope, but very little depth of gameplay. It was panned on release due to under-delivering on features, but has recently received a couple of fairly major content patches. I got quite a few hours of gameplay out of it when it was first released before getting bored, and can't say I didn't get my money's worth. I haven't played it since then, so I don't know whether the updates correct its issues.
Elite Dangerous does a much better job of simulating a living galaxy, and it helps that it's
our galaxy, reasonably well modeled. It is very much a case of making your own fun, but there's a lot to work with and I got several months of gameplay out of it before I got bored, then went back a year later and got several more decent weeks' worth of play.
It suffers from a fairly brutal multiplayer scene, without any real policing if your preference is just to play co-operatively, and even years after release it remains constantly a work-in-progress, with features that were originally promised in the kickstarter still being incrementally introduced.
BTW, is
EVE Online also worth a mention in this discussion or is that an entirely different type of game altogether?
-G
EVE online takes a somewhat different approach, with a lot of things to micromanage. Its combat style is more like that of traditional MMOs, and whilst it is possible to become heavily invested in its universe, getting the most out of it requires you to play it more like a job than a game. I only played it for a few weeks way back in the day, but I don't think the gameplay has changed significantly over the years.