Heavyweights have been the weakest original division, whatever you consider, skills, cleverness or accomplishments, so it doesn't say much to me.
Tommy Ryan, Kid McCoy, Stanley Ketchel, Mike Gibbons, Harry Greb, Mickey Walker, Ray Robinson can be considered for P4P top rankings.
Let's start from the other edge. Fitzsimmons should be ranked lower than Jeffries in heavyweight ratings, agreed? How many ATG hw's can you name who were no worse than Jeffries, only 3 (to fit Fitzsimmons in top 5)?
Not even I rate Fitzsimmons in the top 5 at heavyweight! Though from Memory quite a few did when he was still around, but that is another story. Still, I dont think it is fair to say that Jeffries definitely 100% rates ahead of Fitzsimmons at heavyweight. A very old Fitzsimmons gave Jeffries everything he could handle before a young and prime Jeffries caught him. Who is to say that a young Fitzsimmons doesnt finish the job. And if he does, where does this place him all time? i dont think that there is a middleweight whoever lived that can claim to have a better record against heavyweights. Probably not a light heavyweight either. To this day, more than 120 years later no middleweight has ever fought in and won a world championship like he did (supermiddleweight if you dont believe his weight at the time). It is also a fact that no light heavyweight (other than Tommy Burns who arguably only won a splintered title) has ever done what he did, which is win a world title. IMO, this is impressive in fact that alone is enough to place him as top 5 p4p. This is before you consider his manner of dominance etc. I will admit that due to him holding the world title and benefitting from the monetary situation that accompanies these titles, he did not necessarilly face the quantity of opponents that Greb and some others did, but the reality is that he did not duck fighters and he showed an extraodinary ability to do things that no other fighter of his size could do. His level of dominance, even without the quantity in the later years was something which no other middleweight has achieved, imo. As an extreme example, if bernard Hopkins were to knock out Vladimir Klitchsko while weighing 168 lbs, do we really need to see him knock out every single middleweight contender to know that his current middleweight dominance extends over the current contenders. Once we accept this proposition, Fitzsimmons dominance is astounding. I think he has to be top 5. I have him at number one, personally, which is where he was universally rated for most of the last century.
Jeffries stopped Fitz in the 11th and 8th rounds. That's within even modern, shortened championship distance. You'd pick a 6-rounder to decide the championship to make it fairer to Fitz? I don't think Fitz got much worse between the Corbett win and the first loss to Jeffries. The Corbett win was by a chance blow, after he was thoroughly outboxed, should we doubt Fitz's superiority over Corbett using the same logic you apply to Jeffries? The rest depends on what you consider a heavyweight. If multiple blown up light heavyweights (when that division didn't exist) are considered equal to true heavyweights and super heavyweights, then his record would be impressive. If you take them for what they were - blown up lhw's, and most of whom weren't too clever or skillful or fast, it's not that impressive.
Except this is a ranking for P4P not exclusively as a heavyweight. The same logic could diminish Langford and that doesn't make a lot of sense.
I personally don't rank Langford in top 10. Using the same logic McGrain tried to apply to Mike Gibbons/Cocoa Kid comparison. Langford didn't show enough consistency during his career. He could look the best fighter in the world in one fight, then give a mediocre performance in the next one, and this happened too often in my opinion.
I think a case can be made that Fitz has more impressive and emphatic wins at heavyweight than Jeffries,that he had more skills and talent and that Jeffries only beat him because of the size and weight disparity.