Pointing out the obvious, but the iPhone only has the touch input, and no physical controls, so it's not going to work as a serious gaming device.
Once the A17 makes its way to the iPad mini, that'll be even closer.
Two egregious examples: The Final Fantasy Pixel Remastered series, and Monster Hunter Stories. The first has controller support on both the PC and consoles, but not on phones (which came out first). The second launched on a console (the 3DS), and has no controller support on the phone.
That caveat alone makes it so frustrating to play games on the phone IME.
So some people are seriously playing it with no physical controls. =)
For "serious" mobile gamers there are devices like the Razer Kishi: https://www.razer.com/mobile-controllers/razer-kishi-v2
On this site people tend to forget that there actually are people under 30 whose only computing device is a phone. They use it for everything.
The touch screen is one of the least-used parts of the Switch. Which is a little disappointing, since it was so heavily and well used on the DS/3DS lines. But so many of the ways Nintendo intends you to use the system, the touchscreen isn't accessible. So games aren't built around it in the same way that it was for their previous handhelds.
And it wouldn't be their first attempt at such hardware:
https://lowendmac.com/2006/apples-pippin-and-bandais-world-m...