If you have the orginal Dissidia, then you should get Dissidia 012, since it adds more characters(Lightning,Vaan,Laguna,Yuna,Kain,Tifa,Prishe,Gilgamesh,Feral Chaos), adds new battle elements(assist system), has DLC(costumes+music packs) and a ton more
Kingdom Hearts Birth by Sleep is a good choice, but if I were you, I would get the English translation of Birth by Sleep Final Mix since it has all the US version has(including English voice acting) plus a lot of new stuff that wasn't in the US version.
I would also recommend Final Fantasy IV The Complete Collection if you've never played FFIV or the After Years. It also includes both the original(SNES) and new(DS) soundtracks.
Finally Castlevania:The Dracula X Chronicles, a remake of Castlevania Rondo of Blood that contains the orignial Rondo of Blood and an upgraded port of Symphony of the Night.