Articuno nailed most of 'em there. though i'd honestly recommend ZHP over Disgaea for a token NIS title.
if you need to pick a single Ys game, make it 7. it's awesome.
if you need to pick a single RPG, make it Legend of Heroes: Trails in the Sky. easily the best RPG on the system, arguably the best handheld RPG period.
also get Tactics Ogre: Let Us Cling Together. it ain't a remake to the level of Zero Mission, but it's the closest thing to reach that point since it.
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The King Wang.
Listen up Urinal Cake. I already have something that tells me if I'm too drunk when I pee on it: My friends. - Colbert.