Hmm. I agree that the pixel count on phones is crazy and making a lot of cameras redundant these days, but it is still all about the glass when it comes to creating high-end images. There's a reason why Zeiss, Canon, Cooke etc have lenses in the 10s of thousands of dollars mark.
Indeed, more pixels doesn't necessarily mean more quality. A Canon 400D (10 Mpixel) with a kit lens has only an effective quality of 6 Mpixel.
And more pixels on a small sensor means bad news in low light. Just see what modern DSLRs a capable of at crazy ISO—phone cameras are nowhere near.
Just curious, how do you figure that? I have a Nikon D90 with an 18-105mm f/3.5-f/5.6 lens.
Lenses have published MTF specs which you can fudge into optical resolution specs. It's a bit subjective, but it works. (MTF curves carry a lot of information, and squashing it into a single lp/mm resolution means drawing a cutoff line on a graph which is inherently curved.) Sometimes you publish a couple different resolution values, for different contrasts. The actual MTF curves are more objective and directly reflect system measurements, which is why those are the ones published, instead of resolution specs which are easier to interpret. You can do the tests yourself at home fairly easily.