Good question. I don't know.  I'll mention a few I really dig. LucasArts, due to gems like TIE Fighter, Dark Forces, Jedi Knight, Fate of Atlantis, Monkey Island-- you get the idea.  Epic [Mega]Games because I really liked their 2D games when I was younger and love the fuck out of their Unreal franchise.  Then they went all dudebro and decided to fuck up their PC titles.  Way to stay classy.  Remedy because they're incredible, despite cancelling the Alan Wake PC version.  Apogee for the oldschool and the memories.  Gearbox for fun expansions, decent ports, bajillions of guns, and saving Duke Nukem.