I didn't say no games from this gen will have longevity, I just don't see them having the longevity as games from last-gen. Wouldn't they have higher player counts than older games if they were going to have said longevity? 2 of the 5 current-gen titles in Steam's top 10 are R6 Siege and Rocket League, neither are hardly bigger games. When MGO3 goes offline, fans are not going to bring that back like they did with MGO2.Bloodborne has a huge community still after 5 years since release.
Overwatch has basically replaced Team Fortress 2
The Witcher 3 still have over a thousand people watching it on twitch right now.
I don't really understand your point. Good games maintain an audience. That's just how it is. Fortnite has been popular for how long now, and will continue to be popular until a better next gen game comes out.
MGSV was the best Metal gear for a lot of people. Uncharted 4 was the best Uncharted for a lot of people, I know people that played the other games BECAUSE of 4. Odyssey was the best Mario for a lot of people, Breath of the Wild best Zelda, Assassin's Creed Odyssey best. So your point falls flat because there are plenty of other examples of games people DO think are the best to counter-balance the stumbles in other games.
Why are you dismissing Indies outright? Disco Elysum might be "small" but it's bigger than any game Indies could have been in generations past. Small developers have gone from having no platform to being some of the most popular games of the year. Undertale, Superhot, Shovel Knight, on and on, those games didn't exist in previous generations in the way they do now. They've gone from being tiny flash game on Newgrounds, to having Steam pages and even major boxes releases sold front shelf at Gamestops and Best Buys.
Battle royale may end up being a fad. Though the battle royale games are hardly the bigger and better, Fortnite is hardly AAA looking, same with PUBG.
Who the hell says MGS5 is the best MGS game? I'm like the biggest MGS fanboy there is (that's what the "mgs" in my name represents) and I didn't even finish MGS5. I can see Uncharted 4 being a lot more popular than my personal opinion of it, but UC2 just dominated the GOTY awards across most publications, UC4 definitely didn't. People still care about AssCreed? It's kinda funny that SkillUp's review thumbnail for Odyssey is literally "Bigger isn't always better". I didn't mention Nintendo games because the thread is about the libraries of PS systems.
Sure, indies can make bigger games than they did before but their games aren't necessarily better because they're bigger. Disco Elysium is basically Warren Spector's One City Block RPG so I don't know how'd you equate to Disco Elysium being great because it's "bigger and better". Hell, it has no combat, no crafting, no loot system, etc. I've been asking for games to eschew combat for years now. Games usually become better when you subtract than when you add. If bigger is better than why isn't The Outer Worlds considered to be a much better game than Disco Elysium? How are the indies like you mentioned (Undertale, Superhot, etc) not unequivocally worse games than AAA games because AAA games are "bigger and better"?