"Emotionally invested" are certainly the words for this game! you already linked to the underworld theme (one of my favorites) but those sequences at the end of every underworld tower - and the accompanying music (www.youtube.com/watch?v=XS8pHm…) - always freakin' gets me. I think my favorite part of the game will always be the world before humans, though. Wandering around the empty world and bringing back all the animals 'n plants 'n such. Almost felt a little lonely when the humans came back and you lose your ability to talk to the animals.
*sniff* I miss this game! I should play it again. Bring out all the feels. I'ma clean it off first though, since you been all makin' out with it. (I'm joking, it was a beautiful moment, man).