#6 Deus Ex
The original and best, but it looks godawful to modern eyes. Someone had to say it. In fact, after talking this game up to a friend who only recently got into video games, when she was finally able to get it running, she was immediately disappointed by how ugly it is.
That’s not a mark against the game – it’s a product of its time, like the rest of these titles are. But with Mankind Divided on the horizon supporting DirectX 12 out of the box, it really would be fantastic to be able to play the original game (set after the events of the modern-era Deus Ex games) as it might be made today.