I think this is mostly due to the fact many of Sony published games are cross-gen games so Sony is not releasing the number from PS5 versions, there is no number for God of War or Horizon, though I think this is also applies to third parties as well

But this is all meaningless, instead of best sellers you can simply look at Sony own reports which are the true representative of the first party split:

In any given fiscal year first party almost never crosses 15% of units sold. Revenue-wise, only 30% of those unit sales turn into revenue, so the split in terms of revenue is more likely in 35/65% split. This highlights the importance of Sony first party, even if they sell significantly less. We should also note Sony releases significantly less relevant games (I will stabilish relevant as able to move 1 million units) than third parties

I think it's an ecosystem that needs both. Sony can't survive from third parties because their cut would not be enough to recover costs. But they need a rich third party support to convince people to buy Playstations, and then spend money on first party games too

So about two-thirds of their software revenue comes from third parties based on your estimate, the large majority of their income, not simply a tool to sell units and first part software.

But the more impactful part is that right now third parties are over 80% of games sold on the system.

Forget worrying about selling first party games for revenue, PS owners would lose 80% of the games they buy, and that's not even including Fortnite and other live-service/f2p games which account for a lot of PS user activity.

What the hell would they even do with the system at that point?

I mean there would have to be a good bunch of those games then. I don't think even Nintendo fans would buy a console for just a handful of games for the whole generation? Or maybe they would, if they don't game that often.
The first party is the reason I go for Sony, but I game so much that I need a constant stream of games coming up. Third party is needed. Sony gives me the best of both worlds, but they would never be able to churn out enough games by themselves to keep me occupied. And one system is ideal, I'd hate to have to get two.

Playstation Studios games are by far the best games made out there IMO, so if I needed to pick any system only for potential exclusives Playstation would definitely be my first pick, not only just a pick.

Their games are the ones I wouldn't want to miss the most.

Yes, walled garden always has a quality advantage.

Only if Playstation started making really cheap hardware, something along the lines of the Switch 1. Furthermore, the games would need to be "true" exclusives, and not released 1-3 years later on Steam.

Cheap Console, true exclusives... i would be in.

Playstation has had some stellar first party games throughout the years, but it wasn't first party that made them what they are. It was third party exclusives that did that. Playstation was for years, the de facto place to play if you cared about third party AAA games, and to this day, when it comes to console games, it's still true, imo. And while I own both a S2 and a PS5, that's still the main reason I bought a PS5. FF 16, for instance, was the game that made me buy in. And soon, when GTA 6 launches, I'm going to be rewarded again.

I would probably buy one at the end of its cycle for cheaper to play those games. I would not get it at launch.

I actually did this with the PS3; I played all my third party games on 360 or Wii that gen as I preferred their controllers, so my PS3 was just for Uncharted, Resistance, Killzone, Motorstorm, etc.

If a new PS console had that level of first party quality and was relatively affordable I'd bite; if not I'd probably wait til the next gen and pick up a cheap pre-owned one for any good stuff I missed.

It's an interesting hypothetical because even consoles like Wii U had third-party games.
Probably not, especially if the games came to PC. I'd just invest in a Gaming PC.
If PS5 had the same first-party line-up it does right now with truly no third-party games, it wouldn't be worth it at the $450 and up asking price.