It’s hard to know for sure, since it's hard to say what the overall best game is, but I can give you some best-selling PS5 games:

Deadline (Top-seller)

Yakuza: Like a Dragon (Top-seller)

Crash Team Racing (Top-seller)

The Last of Us Part II (Top-seller)

Kingdom Hearts 3 (Top-seller)

Horizon Zero Dawn (Top-seller)

The Witcher 3: Wild Hunt (Top-seller)

State of Decay 2 (Top-seller)

Control (Top-seller)

Disintegration (Top-seller)

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assitant
Do you have any favorites you’d like me to check out?
assistant
What are some of the best PlayStation 5 games?
user
Hmm, I can give you a few suggestions, which I’ll list out below.  If you give me some keywords you like, I could look up more specific games.
assistant
I'm not worried about specific games or specific genres. I was just wondering about the best overall games if you know of any.
user