Game series you like but still have not played part of the series?

[kupomogli]

Grandia - haven't played Grandia 3 or the unlocalized Gameboy game
Ogre Battle - the NeoGeo Pocket Color game.
Yakuza - Black Panther Yakuza 1 and 2, and Yakuza 5
Phantasy Star Online - I haven't played Episode 4, Zero, or Online 2
Wild ARMs - I own but haven't played Wild ARMs 5