There will never be a good adaptaion of DX
Nobody would produce this :
Deus Ex has a political plot that speaks about secessionism, global conspiracy, population control, etc. nobody in hollywood would now produce a film with such themes.
A good film based on dx would have some action scenes but would be a sci-fi political movie. and with themes that are totally against the good way of thinking of our global capitalist society. how could american investors produce a film in which the hero joins a terrorist secessionist faction, in which the homeland security can be seen as the bad guys.
This film would imply an enourmous budget (scenery, CGI) which means no independent production.
an european production would have very bad reviews by american medias they'd be like "this is how you see our country ? we'll boycott your movie". commercial failure.
a solution : do an action movie and remove all subversive scenaristic elements : it would suck.
or move the american part of the plot to another place in the world : it would lost a big part of its interests, the symbols (like the beheaded liberty statue, the secessionists, all the existing or imaginary American agencies, etc) are too strong images to be replaced by european/asian equivalents.
other possibility : emphasize a lot on the dystopian situation. but it would lose its credibility.