Indeed, arcs are something that we don't see enough of in video games today. One of my favorite game series of all time, Kingdom Hearts, yields absolutely no arc whatsoever. By the end of game Three, Sora is still the same naive, good-shall-triumph, heart-of-the-cards child that he was at the start of game One. What makes Kingdom Hearts even more infuriating is that everyone EXCEPT Sora gets their own arc. Jack Skellington goes from a man (skeleton?) lost in his own delusions of grandeur, oblivious to the impact his actions have on those who love him, to a reformed leader willing to accept advice from those techincally "below" him. They copy Simba's story arc wholesale from his movie. Riku, once a child whose only desire is to escape from a place he finds oppressive, ends the game as a young man who realises that what he once thought was a prison was really where he wanted to be the whole time. Cloud... never mind. Cloud just angsts his way through both games. To watch all the character growth that goes on around the character, while he himself his immune to any kind of development, is truely infuriating.
But, regarding the chemistry between the two leads in PoP Sands, I am reminded, oddly, of Disney's "The Rescuers" for the same reason. Despite the romance being between two mice, their dialogue and pacing as they go from perfect strangers to lovebirds is amazingly natural. It rises up a scale, going from "strangers" to "people who work together" to "friends" to "more then friends" to "love" very naturally. It doesn't cop out with a song like in "Beauty and the Beast", it doesn't mash two dolls together and say "they love each other now" like they do in "Sleeping Beauty". It is a very natural (that word again) progression, and I love the movie for it.