I've seen the figure tossed about that first party accounted for 19.7% of software sold on PlayStation last FY. That's not an insignificant amount of content when you consider just how much third party content is on the platform as well. They are aiming to increase that percentage through all the growth they've done and their new initiatives.
First party has definitely been there this gen. The only way to have a shot at saying it's been lacking is with the silly argument that "cross gen games don't count!" Of course cross-gen games do very much count, so their output hasn't been lacking. I'd say it's slowed down, but that can be attributed to pandemic delays pushing everything back around a year or so, there isn't much they could have done about that. Just to illustrate SIE published games since the PS5 launch:
Spider-Man Remastered
Spider-Man Miles Morales
Demon's Souls
Sackboy A Big Adventure
Destruction All-Stars
Astro's Playroom
Ratchet & Clank Rift Apart
MLB21
MLB22
MLB23
Returnal
Death Stranding Director's Cut
Ghost of Tsushima Director's Cut
The Last of Us Part 1
Gran Turismo 7
Horizon Forbidden West
God of War Ragnarok
Horizon Call of the Mountain
Horizon Burning Shores
Destiny 2 Lightfall
Firewall Ultra
Spider-Man 2 releasing this October
That's an average of just over 7 games a year and that was almost entirely during the pandemic. We should see things pick up massively now that we're in a post-pandemic situation and from my own estimates I think we're looking at 10+ games published by SIE each year starting in 2024.
Not trying to be a Debbie downer, but let's be super blunt and honest here. Most of those releases have been re-releases of existing PS4 titles ported over to PS5 with some additional visual features and bonus content.
Spiderman Remastered and Miles Morales are not new games or brand new releases for PS5. They are additions of existing games for those who want the best possible experience. This is not a full new AAA 1st party release. Sorry, but that's just a fact. Same with Death Stranding and Ghost of Tshusima.
MLB the show is available on a different platform. Wouldn't count this either. Death Stranding is on PC Game Pass.
God of War Ragnarok, GT7 and Horizon Forbidden West while are fantastic games in their own right are cross-gen titles that have been in development since original games came out in their respect years for PS4. The PS5 version is just a better experience, that's it. They are not new exclusive titles to the portfolio of the PS5 generation.
Horizon Burning Shores is a weird one, because it's a DLC that's only available on PS5 but is not a full fledged game since it has less content.l than a full sequel wouldm Call of the Mountain is a VR exclusive and very few people are in the VR niche.
The only true exclusive releases PS5 has under its new generation portfolio is Demon's Souls, Ratchet and Clank A Rift Apart and Returnal. Spiderman 2 is the next one and that is going to be a total of 4 and we are about mark the 3rd year anniversary here in November. Yes, there is also The Last of Us Part 1 that is a remake of a decade old game. Nothing new again.
Destiny 2 Lightfall is available on all platforms despite it being a first party game. It's still not an exclusive to Sony. They just own the right to it and let bungie release it everywhere else. If Destiny 2 went purely exclusive for Sony, the game would die. GAAS titles rely on high player retention and as many players as possible, they cannot afford not to multi release.
After Spiderman, the next big exclusive is Wolverine that we know off and Death Stranding 2. But again Death Stranding is also in a weird situation due to how Kojima and Sony handled the PC version/game pass with that game.
Of course there is ND, SSM but we haven't see anything and we have to wait.