I'm getting them both, XIII and XIII Versus.

The way they presented the story of Versus in the trailers with the footage + music was more like an actual story than throwing together some battle scenes and walking through the forest. I am really psyched about both of them, however, as both XIII and Versus have captured my attention in their own ways. At this point, I think, story-wise, I'm more interested in Versus.

Hmm, according to the Encarta Dictionary

Since it's said that both games are set in the same world but they apparently have no conection at all, we can't use the first definition, because it would suppose that both storylines are intertwine (and thus, each story 'fights' against the other one.

But if we take the second definition we can say that hte game is an 'alternative' to the first one....If both stories are supposed to take place in the same world, all I can think of is that each story takes place in a parallel universe, both featuring the same world. Say, the FFXIII world is more magic-oriented while the FF Versus XIII is more machine-oriented....This is just a guess though