IMO - There's a few games that match it, but nothing "in the same category". Braid, Portal, Stanley Parable come to mind. (Also what I hear about Baldur's Gate 3, but I haven't played.)

But the depth of character, discussions on morality - I still reference the MJ12/Illuminati portrayal from Deus Ex as a discussion on leadership and morality - the depth of gameplay, the way it created a feel of a much bigger, open world.