Both with PlayStation and with Xbox, the recent free games haven't exactly been AAA. That changes with the June PlayStation Plus line-up. 'Metal Gear Solid V: Ground Zeroes' (review here), a game well worth playing, especially when free, leads the charge on the PS4.
Also on the PS4, the excellent strategy title (think 'Advance Wars') 'Skulls of the Shogun: Bone-A-Fide Edition' is free in June.
Meanwhile, 'Super Exploding Zoo' is free for both PS Vita & PS4. As is 'Futuridium EP Deluxe.'