The Ar tonelico series is in my opinion arguably the best RPG games I have played.
1) I own the OSTs to all 3 games. When I play them, I get an elation doing so. I got emotional when I booted up Part 3 of the series because I knew it was the last. I also pre-ordered this game and the last after playing the first.
2) It is a single player RPG which fits my gaming style.
3) All parts of it made it fun. Combat, background music, synthesizing, diving into the Reyvateils, and earning costumes.
4) I want all 3 on GOG because this would likely be the only place other than a PS2/PS3 to play them.
Final Point: I will be adding in my two cents on the other two games as well.
I forgot to mention the game was shipped to me and I received it on my birthday which was a bonus on top of the rest.