Without mentioning that the levels on New York are one of the best designed levels I played on a hybrid FPS/RPG , Hong Kong isn't bad but the story takes a nose dive after you leave UNATCO (it is a big failure on roleplaying you being railroaded into not being able to remain at UNATCO, what I don't understand to this day), the whole Paris section is absolutely dreadful, it doesn't even seem to belong on the same game. Really is one of the best RPGs made but masterpiece? Nope.Deus Ex is one of my favorite games but it sure as shit is not a masterpiece if going by the definition that a masterpiece is an as-close-as-possible-to-perfect work.
I would consider that if the quality on level design was sustained through the whole game and you could remain at UNATCO.
Imho time hasn't been kind to Deus Ex either, and if one is trying to define 'masterpiece' then an engine that can age gracefully could arguably be part of it. I have very very fond memories of the Hong Kong section, mostly the gameplay (didn't like Miss Chow, threw her out the window, and was amazed at how the game just dealt with it, including the people in the street below being in a state of panic when I came out of the building afterwards), but also the whole look and feel of the place. Then... watched the wife play through the game a couple years ago and could hardly believe that ugly empty bad FPS level was what all these memories came from.
There's a lot to be said for good raster art or more artistic 3d rendering techniques (low poly, cel shading...) in order to withstand the ravages of time. For another cyberpunk comparison, the HBS Shadowrun games will imho maintain a lot of their appeal over time when Deus Ex will simply become harder and harder for new gamers to play.