The PlayStation plus part is stale, imo, as I'm not much of a fighting game fan. Or a racing game fan. Or a 3rd Person Shooter fan. Gravity Rush was great, but I think they're hell bent on making sure everyone knows that. It's been free for months! Megaman is sweet though. At least I have no reason not try Virtue's Last Reward one of these days. So really, the pickings are grand if you want to amass the great mountain that is the backlog.
Gravity Rush has been there for months because they always have a set of free games that stay the same for a full year (so they can use those games in major advertisements). For the Vita, it's Gravity Rush, Uncharted, and Wipeout. The 12-months expires next month though so it should be interesting to see what they replace them with (and if you haven't already downloaded them to activate them in your PS+ account be sure to do that now so you keep them after the switch).
As far as the Vita's prospects, I'll admit that there's not a lot in the way of big name games coming up soon but I'm excited for Ys Celceta, FFX HD, and Tearaway, and I've gotten plenty of use out of my Vita (mostly Persona 4 Golden, Gravity Rush, and DJ Max Technika Tune) so far.