Oh this discussion is fun! Art and art history/styles being one of my favourite topics.
I would assume the Art Directors decide the overall style of the game that they're aiming for, and the storyboard/concept artists take it from there, then through to the final 3D artists and renders.
BG3 art style is incredible and continues to amaze me. Slightly stylized, of course, but strikes me as very realistic when it comes to faces and overall character designs. The artists have done an incredible job on this game.
The older games would have been stylized by necessity.
You will also find particular colour schemes favoured in some games, and indeed some movies. For a period of time a few years ago, lot of movies came out with everything tinted yellow-orange/teal-blue (complementary contrast colours). This article mentions this used in games as well: https://tvtropes.org/pmwiki/pmwiki.php/Main/OrangeBlueContrast
