I'd say Neptunia, but let's face it... I don't have 400+ hours instilled into either of the two games, and I definitely haven't played them more than 30+ times.
That said, Tales of Vesperia.
Around 40-ish playthroughs between both versions, PS3/360, and countless hours of fun ~
It is by far the best JRPG I've played this console generation.
Pore, he is MIZUMikomi. Mizu is water. Water is formless, constantly changing shape, adapting to the surroundings... To succeed in life, one must be formless, like water...