They made Vita versions of almost all their big franchises and several vita exclusive IPs. Not sure what else they could have done.
Come on now. Not only are some of these trash (Resistance, Playstation All-Stars, Little Deviants, Reality Fighters), a lot of these are also just ports of PS2 or PS3 games. On PSP you had an exclusive God of War and an exclusive Ratchet & Clank and not a collection of the oldies. Some of those may got ported to PS2 later on, but on the Vita it was usually vice versa - first on PS3, then on Vita.
Now its definitely nice to have PS2/PS3 games on the go and on a handheld form factor, its not like a God of War collection doesn't have value or something, but that's more of a bonus then a real substitute for a proper exclusive. Imagine Nintendo would've released Mario 3D Allstars and I mean just Mario 3D Allstars, and not Odyssey. The Jak & Daxter collection wasn't even good, much worse then on PS3 and even with the weaker hardware in mind it was a poor port. Which is a fate a lot of Vita conversions suffered from. Some people cry about the Switch... compared to games like Borderlands 2 on Vita even the sloppiest Switch conversions are a match made in heaven. Not to mention the Switch in general has a much bigger library.
Its also important to point out what failed and what missed out. Not all of those are developed by Sony, but most are at the very least synonymous with the PlayStation brand and could've sold units:
Failed:
- Ridge Racer
- Call of Duty
- Touch My Katamari
- Silent Hill: Book of Memories (PSP got Origins which was exclusive for a while and a port of Shattered Memories)
Missed:
- Gran Turismo
- GTA, not even a port of an older GTA, while PSP had two exclusive GTA games and a port of Chinatown Wars.
- exclusive Metal Gear Solid
- the only Tekken game on Vita was Street Fighter X Tekken, the PSP had an updated port of Tekken 5 and one of Tekken 6
- Syphon Filter
- PSP had exclusive Final Fantasy, Vita only had a port of Final Fantasy X and X2
- Socom
- Kingdom Hearts
- Monster Hunter
- Motostorm
- Twisted Metal
- Tomb Raider
- Ace Combat
The PSP had a pretty varied library of games with tons of big names and decent support by Sony. With the Vita they weren't able to release games in a similar fashion. There were only few exclusives. Most of the PSP library didn't receive sequels on the Vita. Big stuff like GTA or Gran Turismo missed out. Games like Call of Duty and Ridge Racer failed hard (especially the later hurts, because Ridge Racer on PSP was a great launch title). Not to mention they lost a ton of games to the 3DS.