The relative strength of gravity and electromagnetic forces is obvious — stand on a sheet of paper, and even with the whole of Earth pulling, your motion is stopped by the electric fields inside that sheet of paper.
This is often phrased as "gravity is the weakest of all forces" or some variant thereof. This seems equivalent to saying "the mass-to-charge ratio of fundamental particles is such that charge dominates".
My problem with phrasing it as "gravity is the weakest" is that different particles have different mass-to-charge ratios: according to this chart on Wikipedia, mass-to-charge ratios vary by over 6 orders of magnitude, even if you exclude massive neutral particles like the neutrinos where gravity is infinitely stronger.
With such a wide range of mass-to-charge ratios, why is the question usually phrased as being about the strength of forces? Why invoke extra dimensions for gravity to leak into (for example) when one also needs to explain an extra factor of -5.588×10^6 between top quarks and electrons? (I'm assuming that infinities would get explained away differently, but perhaps not?)
(Hope this isn't a duplicate, my searching mainly showed a lot of "why is gravity weak?" type questions, which isn't what I'm curious about — I want to know why phrasing it like that is seen as the best way of thinking about the problem).