i have a ps2

Sure, play the Atlier series as well.

Ar Tonelico 1 is ok
Ar Tonelico 2 is good, make sure you play it with the retranslation/bugfix patch though
Ar Tonelico 3 (aka "Qoga") sucks massive donkey dick and killed off the original series for a reason
Ciel Nosurge is ok but gets points for sheer weirdness (gameplay-wise, I think I heard they removed the gameplay in the offline version though)
Ar Nosurge is somewhere between ok and good