Whenever these discussions come up, while I agree that the PSP had a wealth of support from major developers that just isn't there on Vita, I feel that the Vita gets no credit for the decent range of downloadable stuff on it. Frozen Synapse, Spelunky, Soldner X, Rogue Legacy, Hotline Miami, Guacamelee, The Swapper, Walking Dead, Terraria, etc etc. It allows western developers to release stuff for it, I can't wait to play Banner Saga for example.
Considering that it also plays the PSP and PSOne digital range, while it's own exclusive library is lacking as a successor, it does allow you to tailor a really nice collection to play on the move.
All the regular complaints (poor exclusive library compared to PSP, memory cards, lack of AAA support) are perfectly valid, but they don't stop it being a great portable gaming system with a large range of compatible games unless you only care for what is new and what is exclusive.