Disgaea has very good entries on the Vita, alongside some very good Super Robot Wars games if you by-chance enjoy mecha.
They're lengthy games that go on as long as you want them too. It sacrifices some of the natural progression elements ala Fire Emblem in case of Disgaea but are incredibly rich and some entries are just full of so much character and fun.
Disgaea 3: Absence of Detention, Disgaea 4: A Promise Revisited are expanded re-releases of the original games that originally launched on PS3 with more content. Absence of Detention specifically is annoyingly still Vita exclusive whilst the rest have enjoyed more modern ports.
All games of these series also aren't *that* connected chronologically, so you can look at which one appeals to you the most and just grab it.