Earlier in the year I used to say that PSP had a better lineup in Japan than Vita did in the territory. Unfortunately, that has really been the case. Obviously you can't fault third parties for doing that as an 18 million userbase is hard to pass up, and even with declining sales I have to imagine Namco Bandai's 70th PSP Gundam game probably isn't breaking the bank at this point. Nor can Sony force them to shift those games to Vita because in some cases (LBX in particular) it just never would've worked for the third party.
Personally, the late-era PSP game that gets me the most is Dissidia 012. No one really asked for a Dissidia 1.5 on PSP, and yet it was made. The game didn't even have the excuse that it was in development for ages (ala The Third Birthday, and Final Fantasy Type-0) but it launched early 2011. I have to wonder why SCE never told Square Enix to push that game as a Vita title since the two are historically pretty close. Final Fantasy works with the demographic that buys SCE hardware, and if it was launch window I imagine most would've excused the midquel-ness of it, as well as the visuals. It's not like SE didn't release Vita games that could easily be mistaken as PSP games during the former's launch window. It also would've given Vita a strong franchise that greatly benefits from local multiplayer. Instead it was released on PSP to middling sales in Japan, and likely non-existent sales in the west.