@Left Hand / Right Hand
and I also recommend(D=digital):
Uncharted: Golden Abyss
Gravity Rush(think if Japan made their own inFamous. at least thats how I see it.)
Wipeout 2048
Tales From Space: Mutant Blobs Attack(D)
Dokuro(Puzzle/Platformer. D)
Treasure of Montezuma Blitz(free-to-play. D)
Sly Cooper: Thieves in Time(I just felt it stood out more as a Vita game)
Assassin's Creed 3: Liberation
Sine Mora(Shoot'em Up. D)
Unit 13(3rd Person Shooter. Not really story focused. Lotta missions tho)
Life of Pixel(PlayStation Mobile, you'll see it at the top in the Vita's PS Store)
Surge(PS Mobile)
Ys: Seven(PSP, a fast paced Action-RPG. D) The new one is coming in September.
Breath of Fire IV(PSOne. It stands up well and the colors/sprites are great on the OLED)
Alundra(PSOne. Similar to BoFIV in terms of quality. Its a old school Zelda type game)
Future one's that have been announced so far:
Soul Sacrifice(4/30. same genre as Monster Hunter but more action focused)
Muramasa Rebirth(6/25)
Dragon's Crown(August it seems)
Ys: Memories of Celceta(9/24)
Killzone: Mercenary(09/17)
Tearaway(from the studio that mad LittleBigPlanet)
Guacamelee(a Metroid-Vania game with Brawler type combat. D) comes this Tuesday
Hotline Miami(this summer. D)
Terraria(D)
Dragon Fantasy: Book 1 & 2(Book 1 is coming this month or next. 2 during the summer. D)
A lot of downloadable games got announced over the past few weeks. and be ready to get a bigger memory card at some point