I have a nice 64gb caard for my vita 
Games I played and completed on this that I'd recommend:
Gravity Rush - fun free-roaming action game.
Metal Gear HD Collection.
Killzone Mercenary - very immersive and at times I forget this is being played on a handheld. very impressive.
DOA 5 + - Plays brilliantly and just so happens to be my favourite fighting game series anyway.
Ninja Gaiden Sigma 1 & 2 - love ninja gaiden and fits small doses of relentless killing on a handheld very nicely.
Wipeout 2048 - best wipeout yet and with the hd & fury pack from the ps3, this game is huge.
Ridge Racer - if you like ridgeracer
BlazBlue - fun 2d fighting game
Soul Sacrifice - monster hunter with good/evil twist.
Uncharted - not far off uncharted 1 on ps3.
Persona 4 - fun RPG.
Virtua tennis - really cheap game from amazon etc. looks better than its ps3 counterpart.
Tearaway - platforming done different.
I have other games, but off the top of my head, those are the ones I return to play time and time again.
Games I played and completed on this that I'd recommend:
Gravity Rush - fun free-roaming action game.
Metal Gear HD Collection.
Killzone Mercenary - very immersive and at times I forget this is being played on a handheld. very impressive.
DOA 5 + - Plays brilliantly and just so happens to be my favourite fighting game series anyway.
Ninja Gaiden Sigma 1 & 2 - love ninja gaiden and fits small doses of relentless killing on a handheld very nicely.
Wipeout 2048 - best wipeout yet and with the hd & fury pack from the ps3, this game is huge.
Ridge Racer - if you like ridgeracer
BlazBlue - fun 2d fighting game
Soul Sacrifice - monster hunter with good/evil twist.
Uncharted - not far off uncharted 1 on ps3.
Persona 4 - fun RPG.
Virtua tennis - really cheap game from amazon etc. looks better than its ps3 counterpart.
Tearaway - platforming done different.
I have other games, but off the top of my head, those are the ones I return to play time and time again.