I remember one thing that got me slightly excited for the Vita before I owned it was seeing footage of Black Ops Declassified - it looked so close to the console game, and the crappy DS port of Black Ops had a Zombies mode! Surely I'll be able to get the game and play some handheld Kino and Five!.. Or... Not! Huge missed opportunity to not go the portable Zombies route - come on, man, even early Android users had it! Why not us?
Certain series were suspiciously absent from the PSP and Vita:
- Dragon Quest was limited to Builders everywhere, and Heroes II in Japan... No classics release of DW7, and no ports of any other games; while the DS got all the Monsters Joker games, 9, and Zenithian trilogy remakes; and 3DS got even more Monsters, new versions of 7 and 8, and a reworked port of 11.
- Mega Man went the parity route, which I never really understood... Yeah, the DS couldn't have handled Maverick Hunter X or Powered Up, but the reverse isn't true for ZX and Star Force. Obviously by the time of the Vita and 3DS, they weren't making new Mega Man games at all anymore... But 3DS still got exclusive access to the Legacy Collection! (Though I guess we still had access to the PS1 ports and other games like X4-6 and Legends 1-TB, so that's still pretty good.)
- Megami Tensei started out with the parity route - DS got Strange Journey and Devil Survivor 1 & 2, while PSP got Persona 1, both 2s (in Japan, we only got Innocent Sin), and a stripped down port of P3... But then next generation, 3DS got remakes of all the DS games, Devil Summoner Soul Hackers, SMT IV & Apocalypse, and Persona Q 1 & 2... A veritable feast, while Vita only got 4 Golden and... The Dancing games, if you count them (I don't). It's odd that the handheld I consider a little more "grown up" gets all the "high schooler friends" games while the kiddy 3DS has all the post-apocalyptic stuff.
(ATLUS in general loved that 3DS because it's a smorgasbord of Etrian Odyssey too; Vita had to make do with Mary Skelter.)
- Sonic evidently really hated the Sony side of the coin, because all we got were the miserable two Rivals games... Nintendo wasn't exactly jam-packed with the series' absolute best (at this point), but they still got Rush, Rush Adventure, Dark Brotherhood, Colors, and a Classics Collection; then 3DS got a scaled-down Generations and some Sonic Boom lites. SEGA really saw no reason whatsoever to bring any of that to the Sony systems, for reasons I'll never fully understand.
In general, the Vita is not as much of a failure for ports as the PS4 and 5 have been (PS1 and PSP classics helped soooooo much), but I think a couple more major exclusive ports could have made a huge difference... Portable versions of inFAMOUS 1 & 2, Demon's Souls, and a crossplay-enabled Fat Princess could have been so much fun. Throw in some better third party stuff like Persona 3 Azure and a console-level-accurate Sonic Generations, and you're in business.