One highlight that I remember was the explanation of mass surveillance being a replacement for less religion in a society. In the past people censored themselves because God was always watching. It was hoped that people would continue to censor themselves because Echelon was always recording and datamining.
https://www.youtube.com/watch?v=1b-bijO3uEw
This was an optional cut scene and not part of the main story -- my friend found this, I never got this cut scene when I played.
I agree that Deus Ex 1 is so special that anything after does not compare. This does not belittle the sequels, its just that the original was so good.
Also: "everytime someone talks about DX1, someone else will install DX1 again" most likely applies here :)
I have played all 4 and loved each one, the charm and freedom of the first may not have been reached with it's successors but I feel like 3 and 4 at least really were fantastic games in their own right.
Sure, the games are flawed ("press a button to pick an ending", immersion breaking boss battles, game breaking launch day bugs, silly DLC and pre-order bonuses) but the world and story they've built are absolutely spot-on. People seem to be quick to forget that the original had its fair share of flaws as well.
Then again, the original had a bunch of other little flaws, but none of them were really dealbreakers.