Okay, still using the best source of strength data I could find, the distribution of men's body weights, and a scant article on a CDC study on the proportion of people who work out, I made a reasonable graph of the distribution of adult male maximum lifting ability.
Now, we know for a fact that there are dudes on this Earth who can lift over 400kg, but this graph only tracks up to the top 0.0001 of men. About 0.00000001 of men can lift 450kg. Also, I have no lifting data for the bottom 0.0034 of men, which should not be a big deal for RPG mechanics development.
Clearly, the average man can deadlift a max of ~80kg, or about 176 lbs. The weakest men can still lift about half that, and men at the 95th percentile can lift about double that. Elite lifters can handle three times as much as an average man, and the strongest men in the world can lift five times as much. Those are some clean, easy guidelines for simulations.
This graph is the predecessor of the top graph, and shows the same data with a different x scale:
I will eventually do this for women. Men tend to lift .42 to .64 more than women of the same body weight and same training. Since men also tend to be heavier and lift weights more often, the women's distribution is probably about half of men's.
I will also compare the strength progressions of popular RPG systems to this real distribution, and rate them by how accurately they simulate real life, as well as by playability, of course. I am using only deadlifts because nearly every system has rules for the maximum amount that a character can lift and not be able to move with, and most systems have no mechanics for other exercises.