I just bought Fruit Ninja for $5 on my PS-Vita
Aside that, I play Guacamelee and Miami Hotline and Sina Mora and whatever other PS+ promotion games come to it. I am very happy with Vita as a device owner.
I do not need anything grander/more than the PSN cross-play games coming to it.
Both CoD Declassified and AC III Liberation were worse games than the free PS+ promotion games I mentioned.