Photopia has been an influential game. The amount of interactivity is small, but the story drives the game along. As has been mentioned, the emotional impact should really be classed as manipulative, but it is effectively done. The author manages to put the player into the skin of a number of different roles and also to make the reader identify with characters at different stages of their lives.
The underlying "story within a story" is pitch-perfect. Probably because it appeals to the wish fulfillment natural to games (or gamers?). The outcome of the game ends up being telegraphed about half way through, but this leads to the emotional punch and drive of the narrative. From then on, it unfolds remorselessly.
The greatness of the game is its ability to remain in mind after one has played it and yet be fresh on replay.
An important game. Emotional reactions will differ, but I would categorize it as touching. (Spoiler - click to show)Few mazes are as satisfying as the one in Photopia. We all have wings...