If you ask me, PS5 only have 3 games: Ratchet and Clank, Demon's Souls Remake (and is a REMAKE from PS3) and Returnal.
And I have to tell you that all of them are Amazing. Returnal is even harder than DS.
Maybe sackboy... Sackboy es great, but you can find it in PS4, the same Spiderman Miles Morales so... they're not "PS5 exclusive games".
Finally... I choose Demon's Souls. I just love the souls games. But If I should recommend one game, I recommend you Ratchet and Clank.
Returnal is a Bullet-Hell Roguelike so, don't play it, you gonna cry a lot.