X-Wing and TIE Fighter, which are the grand-daddies of Freespace.
And of course the
Wing Commander series (+ Privateer), although I find them hardly playable (didn't like them that much in the past either).
Star Control needs to be mentioned too.
When it comes to 4X there is still no better game (IMO) than
Master of Orion 2 (the MoO game is pretty good, though, and indeed very pretty ;-))
When we leave GOG for a moment we can't ignore the legendary Elite and its sequels Frontier and First Encounters. Of Frontier there are great free remakes here:
https://pioneerspacesim.net/#slide0 and here
https://sourceforge.net/projects/pioneersp/
And there is, as mentioned above, Freelancer.