Imho, they're two completely different games.
'No Man's Sky' is a more like a piece of art than an actual game. I think, it should mostly appeal to players who enjoyed 'Shadow of the Colossus' or other titles from Fumio Ueda.
'Elite: Dangerous' is the MMO version and a technical update of 'Elite: Frontier'. So, it should appeal to Elite fans, obviously.
And 'Star Citizen'? Knowing Chris Robert's megalomania, this game will never be finished. Sink money in it, if you have to, but don't expect to get much out of it.
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.
I so want Elite Dangerous on PSVR.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.