The WiiU failed as well.
That said, the Vita was a amazing device

I would argue that the biggest failure of the PSV is that is has not secured the future of the Playstation portable brand and concept.

Will SCE continue in the mobile space with its own hardware/software ecosystem by means of a successor platform? If the answer is no, I find it hard to come up with a convincing argument that the PSV was successful in terms of original intent rather than by adjusting the goal posts.

- It sold better than X platform
- It hasn't been pulled from the market
- It made a net profit
- The hardware is profitable
- It has a good catalog of games

None of these equate to the sustained market impact much less market growth of the Playstation portable brand/concept.

The market niche that was occupied by the PSP was effectively eaten up by Android and iOS. The PSV has become a small niche ecosystem that will not see growth and will either continue to be a legacy platform to eventually die a slow death, or it will be replaced by a Playstation Mobile concept.

The two main things keeping Nintendo portables alive are their IPs and the children's market, with only a smaller segment of nostalgia consumers (i.e. Millennials who still play old style Pokemon).