Honestly, DX3 is easily fitted into the original as by the time DX1 had happened, things are falling apart, whereas DX3 is really at the apex of things before it goes to **** (this game being set 25 years before DX1). The particular art style works exceptionally well with this idea of a civilization gone to excess before a collapse.
And since when did drab become the only idea of "realistic"? The greeks had an exceptionally stylized culture (for those with the cash, obviously) with ridiculously gaudy color schemes and excess of clothing and architecture etc. flourished during the renaissance with excessive decoration. Why does that sort of style being projected into the future=non-realistic? And again, the slip from neo-renaissance to utilitarian makes sense in the DX timeline, as in that span there were plagues, earthquakes and successions throughout the country.
As far as originality, while there is certainly a decent helping of Blade Runner, with its dense citiscapes it is a unique and original deviation in terms of actual aesthetics (BR being more a run-down, ad-centric society). There is certainly no other game that does this style and while there are a FEW movies that have a similar idea, I can't think of a single thing this is really derivative of.
Lastly: I've said it before, Deus Ex was full of interesting ideas that were handled extremely poorly and while I'm not a fan of 3rd person views at all in FPSs (one of my biggest pet peeves, actually), I think this game looks to replicate the massive choice and playstyle variations that the original did, only far far better.
~Jason
edit:
Looks alright, I never played the original Deus Ex games, though I might have to look into them. Are they very good?
They're worth playing, as the DX1 is MASSIVELY important in its originality of playstyle, though since so many games have utilized various concepts far far better since then (in more compartmentalized ways) it may be difficult to force yourself through.