It is a smart pilot that takes a lot of approaches we've seen before and assembles them in a compelling whole.
I like the idea that this is built up from the original Westworld in the same way Jurassic World was built up from Jurassic Park.
Also, there is a strong influence of DARK CITY in this in that the "hosts" are implanted with a variety of personalities so that one body may actually have a history of several different lives. This also brings up the natural "wheel of karma" metaphor that Dark City played with. Enlightenment or "Gnosis" is achieved when one realizes that all of the lives one has lived are essentially false.
The "hosts" are far more sympathetic than the guests (parasites) or the overseers which is a big change from the original movie where the guests caught in the malfunctioning park were the protagonists even though hubris may have been at the heart of their troubles. Playing God is still the primary tragic flaw of the story, but in this case what's interesting is that the "God" of this world sees his apotheosis (or the human race's apotheosis) as a dead end.
Of course, the discussion of evolution and mistakes also brings up the idea that even if they did achieve the ultimate mastery over death and life that Ford resigns himself to, there is still a dark space unknown that could surprise them. It touches upon the theological question of how an omnipotent, all-powerful being could overcome its own boredom.
Also, in the case of the Ed Harris "guest," he certainly does seem to be playing Satan to Hopkins' Jehovah. He's looking for something in Westworld and its systems that its creator(s) have overlooked.
On top of all the philosophical gems in the story, I think the characters were also captivating on an emotional level - even though their emotions are clearly shown to be programmed.