RE: What kind of games could "save" the Vita? Presumably we're operating on the assumption that the kind of games that did well on PSP would do on Vita, and that to have PSP-like success, the Vita should have a PSP-like library. In reality there could be a new trend, one which couldn't simply be predicted by looking at what did well on the PSP. But assuming the PSP->Vita link and isolating for games selling above 200k on PSP, here's what we get
Monster Hunter (+ similar games like God Eater)
Final Fantasy (+ spinoffs like Dissidia, Tactics)
Kingdom Hearts
Metal Gear Solid
Phantasy Star
Tales
Gundam / Super Robot Wars
Musou
Other:
Sports (Baseball, Soccer, Hot Shots Golf)
Games related to Idols (AKB48 games, Hatsune Miku)
Racing Games (GTP, Ridge Racer)
One-offs or misc: Little Battlers, Yakuza, Taiko Drum Master, The Third Birthday, Persona 3 Portable, Star Ocean remake