This question really deserves categories.
Erie is excluded for obvious reasons.
But then all of your genuinely big waters that stay cold produce impressive average size, and a large portion of lunkers. The Big D, the Lehigh, the Allegheny (below Kinzua), and I suppose you could throw the Yough in there. In many cases these aren't wild fish, but fingerling stocked or held over for years, I think that counts.
Then you got your limestoners. I won't name names, but there's a high number of lunkers in many of them, some more than others. Those lunkers may or may not surpass the lunkers in the streams, err rivers, mentioned above, but I don't think the average size compares.
And then you have the small stream fishing, sometimes brookie streams and sometimes stocked. The occasional big brown is in there, and these fish are true trophies in that they dwarf all of the other fish around them. They aren't the top end of the size distribution, they're on a separate curve compared to the rest of the stream. I haven't focused on these fish very much, so I'm no expert. But where I've seen them they seem to have something in common. They are in, or near, the truly marginal area of a high productivity bigger water. I say "truly" marginal, because sometimes we use the term marginal when we really mean warmwater/seasonal fishery, but those fisheries rarely produce big fish. No, I'm talking about the iffy area, the lower end of true year round trout water, or nearby tributaries which act as summertime sanctuaries. This water has plenty of food due to size, but few trout because there just isn't enough cold spots to support a high population. As a result, when the water temp is optimum for trout (and bass ain't feeding then), the few trout there are get it all to themselves to gorge.
