Arcadia is a sort of Eden in pastoral elegy. The Romans and the Greeks used it as the name for an idyllic place where shepherds lounge around composing beautiful verse in the verdant fields while the sheep gambol around them. Arcadia is a real place in Greece on the Pelopponesian peninsula. When the Renaissance rolled around and people rediscovered the Classics, Vergil became popular once more and so did pastoral elegy. It was a natural fit with the Christian world since the word pastor is Latin for 'shepherd' and the ministers of the Church were after all 'shepherds of men'. The rustic, natural world of innocence in Arcadia is a sort of Eden.
That being said, when Arcadia becomes the last decent place on earth in Resident Evil, you expect it to be a rustic sort of paradise. If one can ignore the evidence of all those airplanes and lack of signs of life, when Alice arrives in Alaska to rejoin her friends, her picking up her notebook and turning to a page on which the words "Et in Arcadia ego" are written should leave you with no doubt. Arcadia is not meant to be a paradise.
For those who do not know, this phrase is famous for being written on a tomb in a Nicholas Poussin painting called 'The Shepherds of Arcadia'. (For a glance at the painting, click here.) It is an ambiguous phrase. It could mean that the person buried in the tomb had also been to Arcadia but, since the tomb seems to have been placed in Arcadia, the general view has been that it is Death that inscribed that line - I exist even in Arcadia.
The word 'et' can mean 'and, even, also'. The verb in this phrase is understood. which is a perfectly acceptable Roman practice. The lack of a verb has lead to an amusing misunderstanding in the Da Vinci Code from the book Holy Blood, Holy Grail that it was based on. Latinists are a dying breed, it is true, but a call to any university ought to scare up at least one to check your facts. Nicholas Poussin is added to the list of mysterious members of the Priory of Sion and 'Et In Arcadia Ego' became a complete sentence that was also an anagram with a hidden message, ignoring the unstated but understood verb.
To return to the movie, since this is Resident Evil after all, you know that she will find Arcadia and the generally accepted interpretation of the phrase, that death exists even here, will ring very and savagely true. I do not want to spoil the movie for anyone but I give it both thumbs up. It might not be Shakespeare but not everything need be great art.