Started a replay of Human Revolution recently, love the game, although I don't know that after Hong Kong (which is an amazing city area for not being open world) it's worth finishing a second playthrough. Tried Mankind Divided when it came out and a number of things about the game just didn't come together for me.
Mankind Divided was better than Human Revolution imo. It's more open and does a better job of making you feel like you're in a real city.
The original Deus Ex is still the best game in the series though. It had an atmosphere that was never fully recaptured in the sequels imo. It was like a cross between Blade Runner and the X-files. It was also ahead of its time back when there were very few FPS-RPG hybrids.