I'm still an iPhone guy, and don't see that changing for a while.
There are a number of reasons. Part of it is simply tight integration with the ecosystem: I can take calls on my Mac, headphones pair easily, that sort of thing.
Performance matters. The iPhone XS I have is consistently faster than Android devices both in terms of raw power and, importantly, in UI. It's wild to me that people accept occasional bouts of stuttering and lag in their Android phones. Heck, I have an Essential Phone with virtually stock Android on my desk and it's odd how often I have to reboot it just because it bogs down for no apparent reason.
Then there's software updates. I'm sorry, but Android's two years of major OS updates (often delayed by months) with only periodic security fixes just strikes me as shoddy, even with Google Play Services filling in some gaps. On an iPhone, you can download every update the millisecond it's ready, and you frequently get four or five years of those updates. This isn't including apps, which tend to get iOS updates first and often run best on Apple's platform.
The screen, camera and speaker quality is also very strong, even if there are areas where other phones do better (I won't doubt that the Pixel 3 takes better pics in some cases, though it also trails at times).
And finally... there's the Apple Watch. Like it or not, it's the best smartwatch on the planet, and I'm not going to give it up just so I can get an Android phone with a higher-res screen or wide-angle camera. You don't realize what you're missing by settling for most Wear OS or Tizen watches.