I'll chime in on this one...
Quantifying strength is sort of a difficult thing. Although very subjective, the real measurement for someone is what can they do with that strength.
To me functional strength is the top of the food chain. If you can deadlift 500 lbs but have to use straps to do it, then it doesn't really mean that much other than you have a strong erector chain. Just hope you don't actually have to use your hands to puck something up that weighs 500 lbs since because your use of straps has probably negated any grip strength you might have gained. So maybe a measurement of what you can do outside of the gym is more appropriate? Can you work harder than the next guy? Can you move big rocks out of your garden? Can you handle that half barrel for the party solo, or do you need help getting it in the house? What about helping push a buddy's car out of the ditch? See where I am going with this?
Then there is the type of strength issue. Are you explosively strong, or do you have better static strength? For example, I can't power clean shit. On an axle press I can get maybe 230 up, but after that I have to use a continental clean (some of that has to do with bar thickness, lack of whip, and that an axle doesn't rotate like an oly bar). Give me a log, however, and I can clean and jerk into the mid to upper 3's, and I can get nearly 300 with a concrete block. The point here is that the method of action of the lift can go a long way in determining strength.
But lets make this a little more simple. If I were pressed to give an opinion on what constitutes say a base intermediate lifter using gym lifts as the metric, I would probably go with something like this (using only a belt and chalk - no straps or suits):
1) 2x bw below parallel squat
2) 1.5x bw bench (with a pause on the chest - no bouncing)
3) bw overhead press
4) 2.5x bw deadlift with no grip aid other than chalk
I say all of that with this caveat. It all depends on how you look doing those lifts. If, for example, to get the 1.5x bw bench you look like a break dancer on the bench and don't have control of the weight, you need to do some more work. Same goes for hitching the dead, or having your form go to shit on the squat.
B-