Somewhat realistically? And outside of Godfall, which has already been announced?
Most will probably be PS5 "enhanced" versions of first-party games already out for PS4, so The Last of Us Part II, Ghost of Tsushima, and Dreams; probably God of War and Spider-Man, as well. Worst case, they may not even be retail releases, either. The enhancements may just be updates or PSN downloads. Doubt it though, as it might count against the launch lineup and make it look thinner.
Actual new games may be Gran Turismo 7 (or perhaps just Sport: Complete Edition, with all free update content on-disc), and perhaps Killzone to be the obligatory first-party next-gen-only launch game made to show what the console can do, like Shadow Fall was. A game from Japan Studio may be likely, as they've been silent since 2018; it's probably a game by Cerny. And maybe Housemarque's battle royale, Stormdivers, which was announced in 2018 and supposed to be out in 2019, but they seem to have pushed it back. Hopefully to change direction away from a BR game.
Outside of that, I don't see anything else coming on day one. Stuff like Ratchet and Clank and what Bluepoint's doing may come within launch window, but not the first day, in my opinion.