To be honest, I don't see the Switch 2 getting all the big most popular AAA games that PS5/SX are getting. The Switch 2 will likely still be quite a bit underpowered compared to those consoles where it would be too difficult to get it to work on Switch 2 for some developers to see it as worth it. For example, it's highly unlikely GTA 6 will ever come to Switch, that game seems to be using every ounce of power the PS5/SX uses for it to be feasible to work on a handheld.
However, I think this time around 3rd party support should be better than the Switch 1, we already have confirmation that the full COD games will come to Switch 2 day in day with the other consoles which is certainly huge, as you can make the case that COD is the most popular franchise right now.
Also, developers this time around now trust making a game for the Switch 2 a lot more now since the Switch concept has proven to be a major success so developers will likely begin developing games right away for Switch 2 unlike how it was for when the Switch 1 first launched since many developers were uncertain/doubtful it would be a success.
We're also approaching a time in gaming where the cost of game development is becoming unsustainably high, this may benefit the Switch 2 as well since developers will be forced to release their games on as many platforms as possible to make up for the astronomical game development costs. So I think that will help Switch 2 get more 3rd party support as well. We've already seen a big developer like Square Enix commit to bringing more games to the Switch just to make up for the rising game development costs.
There's also rumors that are suggesting the Switch 2 to be quite impressive in specs for a handheld, with the rumors suggesting it'll be somewhat close to a Series S in power which can definitely help make porting next gen games much easier to Switch 2 if the rumors are true.
However, despite all this I don't necessarily think the Switch 2 will get every big 3rd party game, there's also still a persistent perception of Nintendo that 3rd party games don't sell as well and that might push away some developers from making games for the Switch 2, that perception is definitely dying in the Switch era but it still exists to some developers. One notable one is EA where they still refuse to bring their biggest games over like Madden, Battlefield, new Need For Speed games, and more.