If you want to know which platform(s) are going to win over the next several years, then you only need to ask three questions. Here they are in order of importance:
1) Does one platform clearly have a much better game library?
2) Which platform is the best value?
3) Does one of these platforms especially appeal to marginal gamers (i.e. "da casualz")?
So I am going to break this up into two categories: A) Sony vs. Nintendo and B) the streaming services and C) Apple Arcade.
A) So if you compare PS5 vs. Switch, both are going to have a good library of games. Switch already does have a good library with plenty more games coming, and we've seen that PS5 will have games coming. Switch is a much better value though. It's cheaper (that's obvious), but portability also makes it a much better value. Switch probably also appeals just a little more to "da casualz" because it's portable and it has some motion control games. But really any system that uses the classic controler scheme doesn't appeal to "da casualz" too much. Overall Switch is going to be the clear winner based on value.
B) Let's take Microsoft vs. Google vs. Amazon on streaming service. Microsoft's service is going to have a much better library of games. They simply have a lot more game studios and every Elder Scrolls fan, for example, is going to want Gamepass simply because of the games. All of these 3 subscriptions services offer a similar value and don't really appeal to "da casualz" because they use the classic controller scheme. Microsoft is going to be the clear winner for the next few years simply because of its game library. Google and Amazon are really going to have to come up with some good exclusive games on their own if they are going to have a chance of competing with Microsoft.
C) Apple Arcade is in a category all on its own. That's because it's the only platform right now that is seriously trying to appeal to "da casualz". Most of its games use either touch screen controls or maybe a simple joystick with buttons. Both of these appeal much more to marginal gamers than the classic controller scheme. That means that Apple Arcade (and gaming in general on the iPhone) is going to continue to be a very profitable business for Apple. This service is not going to be a big deal anytime soon, but in 10+ years it may end up being the dominant player in gaming. In gaming, 10 years is a huge amount of time. It's the difference between Final Fantasy 1 and Final Fantasy 7. Add another 10 years and you are in the FF12/13 era. Give Apple enough time to make tons of bank with "da casualz" and their games are going to be much better and more sophisticated. They will grow into a serious force to be reckoned with. It won't happen anytime soon, but don't take your eyes off of them either.