If you're into retro-gaming, Starflight and Starflight II were both excellent.
https://en.m.wikipedia.org/wiki/Starflight
https://en.m.wikipedia.org/wiki/Starflight_2:_Trade_Routes_of_the_Cloud_Nebula
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If you're into retro-gaming, Starflight and Starflight II were both excellent.
https://en.m.wikipedia.org/wiki/Starflight
https://en.m.wikipedia.org/wiki/Starflight_2:_Trade_Routes_of_the_Cloud_Nebula
so for something completely different and focusing solely on the "size" aspect:
the biggest, that i am aware of, game in terms of sheer SIZE involved, is Stellaris:
it's a paradox grand strategy game, not first person at all, so completely different from the other recommendations and probably nothing to do with what you asked for...but if you want something truly MASSIVE...well...can't go much larger than galaxy spanning all out war involving gigantic fleets and armies!
so if power fantasies is something you're interested in, maybe take a look! it's pretty easy to get into, but has a lot of depth (but no requirement) to master later on! and it has a lot of settings regarding game speed and difficulty to tailor it to your tastes.
and mods, god help me, the mods; play a couple hours to get to know the game, then definitely get Gigastructural Engineering from the workshop. short list of ridiculous engineering:
(sidenote: the new DLC subscription on steam is...kinda worth it honestly. not the worst idea, especially to just try it out for a couple hours. i was extremely skeptical, but it's kinda, surprisingly, less predatory than the previous "we'll release 2 20$ DLCs, and 1 30/40$ DLC per year" model...)
Star Citizen is the only modern game that I've got any hope for. It's still years from being a proper game, but in the meantime you can have a surprising amount of fun in the persistent universe, assuming you can run it at acceptable framerates.
It gets a ton of hate, which I think is pretty unjustified given that it's the single most ambitious gaming project ever, and the progress they've made with in-house tools is frankly amazing. Just don't go dropping hundreds on ships and you won't have anything to regret.