The only big jrpg series that i can think of without going too obscure for Sony are Dark Cloud and Wild Arms. Dark Cloud got a sequel and sold pretty well in the early ps2 days. Wild Arms got 5 games, a remake, and a couple of spin-offs big in Japan. Hopefully these two franchise get implemented here in at leat one way. Still like the character roster.
Disgaea: One of the best selling JRPG series on the PS2. Three sequels, two remakes of the first game, a remake of the second and third, and two awesome spin-off games as well as the characters being featured in various cross-overs.
I was talking about 1st party titles not 3rd party. The games that Sony owns, people are quickly jumping to use 3rd party and doesn't realized some 1st party franchises are still missing. Though i want a Disgaea rep in this game too.