There's some bangers on ps+. I'm a pc gamer but I've peeked (extensively) at the catalogue and while I still feel Xbox game pass is better value for money, here are some:

Abzu: beautiful game about exploring an abandoned underwater environment

Bloodborne: not "hidden" but a must play

Concrete Genie: Cute little game about grafitti creatures

Dandara: a unique platformer with a great style

Dead Cells: fantastic roguelike

Ghostrunner: amazing cyberpunk parkour game. If you like movement, you'll love it.

Everspace: great arcade space game.

INSIDE: wonderful little game that will have you thinking about what it's story really meant

Magicka: incredibly silly magic game

My Friend Pedro: gunslinging slow motion stunt combat action

Moonlighter: roguelike shopkeeping game, think Reccetear

Party Hard: stealth party killing spree action

Spiritfarer: beatiful game about helping the dead find peace before moving on

Vermintide 2: one of the best horde games out there.

Other ones that are less hidden gems but I conside must plays or at least worth checking out: Bloodborne, Death Stranding, Dishonored, Doom, the Middle Earth games, Shadow of the Collosus

It's hard to recommend games to someone you know nothing about.

I love a game, that I can't recall the name. It's a top down shooter. A plane/ship. Waves of bad guys. Power ups. If I remember I'll come back.