This is kinda hard to explain properly, since the best part of Ar tonelico are the music, world setting and story. You can play Ar noSurge without playing Ar tonelico, but it requires a bit of reading of the previous games to get a grip at what's the world building. It's pretty deep and thing will get over your head a lot if you go into Ar noSurge blindly. I think kiryogi could help you better at this in
this thread, since it's been a long time from the last time I played Ar tonelico.
Basically, it revolve around Reyvateil, a race that could transform song into magical energy, so the franchise will heavily involved in music, and that's where the game shines the best. Also, there are different ending of each game depend on the heroine's route you aim for, and because of the Dive system, where you go into the heroine's inner world by diving to deepen the bond and unlock her magic potential. By doing that, the game helps you to understand everyone's mind and characteristic better, thus you heavily emotion invest on the character much more than usual RPG (think of social link of Persona, just deeper).
Briefly, that would be the surface of thing to know what the game is about. I'd go nut over the Hymnos, the kind of made up language used throughout the series, but that will scare you guys so I will stop here, lol, and be back when you guys have more interest. I'll borrow kiryogi's bonus list, since I can't access youtube right now.
https://www.youtube.com/watch?v=eoicX3RPf5Q
https://www.youtube.com/watch?v=ZEkfQQMiu64
https://www.youtube.com/watch?v=XP6jw6ToAIc
https://www.youtube.com/watch?v=aFx0QEl8-Ls
https://www.youtube.com/watch?v=IiOJGNT1j8s
Usually I'd say people who keep saying "moe" don't even know what's moe is, but I guess that's not the case when you're in Vita thread. There are 2 kind of moe-centric product, one involve in shallow experience and the point is selling the girl's appearance for quick cash grab (lot of mobile card games, or the Love Live Vita game recently), the other use moe as the theme for their game, like Neptunia (where everything is cute girl), or Senran Kagura (life and hometown as the base, and are improved through gameplay) or Dungeon Traveller 2 (fanservice gallore, with good gameplay). You see, in these examples, just think the moe is a theme, like when they are making a game with mecha theme, or world war theme.
The problem is when people associate every moe game as a shallow cash grabbing game, and trying to dismiss it as soon as they see a cute girl image. That's the same as saying all FPS are shit because all you are doing is shooting at thing.
My point is, don't dismiss the game as bad game just because its theme. That's why place like GAF exists so you can get various impression from people who have played the games.