Well, that was quick! The iPhone 8 Plus had a short reign at camera testing outfit DxOMark as "the best smartphone camera we've ever tested" — the Galaxy Note 8 tied it after only a few weeks. And now Google's Pixel 2 has bested them both.
Citing excellent video performance, great color and scene reproduction, incredibly fast and accurate autofocus, and good (if not great) artificial background blur, the Pixel 2 ended up with an aggregate score of 98, beating out the other two, which had tied at 94.
Now, the folks at DxOMark are experts, and I trust their determination here. There's no doubt the Pixel 2 has an amazing camera. But as with other aggregate scores for things like DSLRs, games, movies and so on, the big number only tells part of the story (especially when it's so close to the other big numbers).
Looking through the sample photos of all these flagship phones, you may find that you prefer the look one creates more than another's — I certainly think Apple's portrait mode looks much better than the others, and its luminance noise in tricky situations is preferable to me. Yet I like the Pixel 2's color reproduction (and on its OLED screen the photos should pop). Yet again the zoom performance of the Note 8 is definitely superior.
What kind of photos do you take? What are your needs as a photographer? Will a zoom be an asset, or do you need an ultra-wide angle? Do you use the flash often? Are you willing to let an HDR mode do the work for you? If your phone is going to be your primary camera, it's worth considering the qualities and shortcomings of that camera as much as the phone's storage, screen resolution, color, and so on.
And lastly, it's pretty clear that cameras are just going to get better from here. If you compare their results to those of a competent mirrorless today (that even with a lens may end up costing far less than a flagship phone) you will find them quite lacking. There's lots of room to improve, and as DxOMark points out, there's no reason their scores can't go above 100.