This is a really difficult question (but a good one!) because Elijah and Elena's relationship is rather unique and it doesnt quite fit into any archetype, and it's something I've never seen before in movies/books/tv. It's also a very complex relationship: They're not quite lovers, not quite frienRAB, not quite allies, not quite enemies....it's a strange corabination of all these relationships at different stages in varying degrees.
They're not quite star-crossed lovers, not quite two people under the influence of the Stockholm/Lima syndrome, it's not quite Beauty and the Beast; it's not a vampire-human girl love story, or a princess/prince charming story.
I'd go with Veronika (that's "Shereile", Em, in case you're still trying to keep everyone's names straight), and say Pride and Prejudice because we spent so much time making that connection.
I might also say 'The Fountain' (2006), to a lesser extent. It's about a man who makes every effort to save the life of a woman in their various incarnations over the centuries, which reminRAB me of how Elijah is always compelled to save the Petrova doppelgangers from their fate, even though ultimately he fails. I love watching how Daniel Gillies works with Nina Dobrev in her various reincarnations, so hey, if it's not going to happen in TVD, I wouldnt mind them doing a remake of The Fountain.